ISC

ISC Commerce Previous Year Question Paper 2019 Solved for Class 12

Maximum Marks: 80
Time allowed: Three hours

• Candidates are allowed additional 15 minutes for only reading the paper. They must NOT start writing during this time.
• Answer Question 1 (Compulsory) from Part I and five questions from Part II, choosing two questions from Section A, two questions from Section B and one question from either Section A or Section B.
• The intended marks for questions or parts of questions are given in brackets [ ].
• Transactions should be recorded in the answer book.
• All calculations should be shown clearly.
• All working, including rough work, should be done on the same page as, and adjacent to the rest of the answer.

Part – I (20 Marks)
Answer all questions.

Question 1. [10 × 2]
Answer briefly each of the questions (i) to (x) :
(i) What is meant by the term Business Environment ?
(ii) State any four short-term sources of finance for a Joint Stock Company.
(iii) Mention any two advantages of e-Banking to the customers.
(iv) Differentiate between Fixed Capital and Working Capital.
(v) “Management is universal’. Comment.
(vi) State any two points of difference between recruitment and selection.
(vii) Explain feedback as a part of the process of communication.
(viii) Mention any two facilitating functions of marketing.
(ix) Name two types of markets on the basis of nature of transactions.
(x) Mr. Kappa has recently purchased a refrigerator from TUTU Enterprises, paying ₹ 30.000 After using it for a day or two, he found mechanical defects in the refrigerator. Immediately, he informed the dealer about the defect but there was no response from the dealer. Mr. Kappa decided to lodge a complaint against TUTU Enterprises.
(a) Which court should Mr. Kappa approach to file a complaint ?
(b) State any one relief the concerned court may order in favour of Mr. Kappa.
Answer:
(i) The business environment is a mixture of complex, dynamic and uncontrollable external factors within which a business is to be operated.

(ii) Short term sources for a Joint Stock company are :

• Public Deposits
• Trade Credits
• Customer Advances
• Factoring

(iii) e-Banking services have the following advantages :

• Customer can do transactions 24 × 7 basis.
• e-Banking transactions are online and almost instantaneous.
• Customer can do transactions from anywhere: from his home or workplace using a computer or laptop or mobile, he has no need to visit his bank branch.

(iv)

(v) Management is universal in the sense that it is a common and essential element in all enterprises. Management is universal in the following sense :

• First, managerial skills are transferable from one person to another.
• Secondly, management skills can be transferred from one organization to another.
• Thirdly, managerial skills can be imported and exported from one country to another.

(vi)

(vii) The observation of the receiver ‘s response is called feedback. It enables the sender to evaluate the effectiveness of the message. Without feedback, two way communications is either ineffective or incomplete. Feedback is the only way to gain receiver’s response and depending on the feedback, sender can take further steps.

(viii) Facilitating functions of marketing are :

• Standardization and grading
• Financing
• Risk taking

(ix) Types of markets on the basis of transactions are :

• Spot markets
• Future markets

(x) (i) District Consumer Forum
(ii) Replacement of product

Part – II (60 Marks)
Answer any five questions

Question 2.
(a) Explain three important characteristics of Management. [3]
(h) Briefly explain any four external factors of Micro environment of business. [4]
(c) What is meant by barriers to communication ? Explain three suitable measures the barriers to effective communication. [5]
Answer:
(a) Management is goal oriented process : Management always aims at achieving the organizational objectives. The functions and activities of manager lead to the achievement of organizational objectives.

Management is Pervasive : Management is a universal phenomenon. The use of management is not only restricted to business firms only but also it is applicable in profit¬making, non-profit-making, business or non-business organizations: even a hospital, school, club and house has to be managed properly.

Management is a continuous process : Management is a continuous process. All the functions of management are performed continuously, for example, planning organizing; staffing, directing and controlling are performed by all the managers all the time.

(b) Four external factors of micro environment of a business are :

• Suppliers : Without a supplier, it is not possible to carry on the business.
• Customers : Customers are another basic requirement to run a business. If no one is buying the products of your business, you will have to close its doors.
• Marketing Intermediaries: Middlemen have a direct impact on your business operation. They could be your distributors, wholesalers and other related people.
• Financiers : Typically, business owners take out a loan to get started and the growth of the business depends upon their ability to obtain additional loans.

(c) There may be many barriers in the process of communication. The intended communication is often disturbed and distorted leading to a condition of misunderstanding and failure of communication. The barriers to effective communication could be of many types like linguistic. psychological, emotional, physical and cultural etc.

Measures to overcome the barriers to effective communication :
Use of Simple Language : Use of simple and clear words should be emphasized. Use of ambiguous words and jargons should be avoided.

Reduction and elimination of noise levels : Noise is the main communication barrier which must be overcome on priority basis. It is essential to identify the source of noise and then eliminate that source.

Active Listening: Listen attentively and carefully. There is a difference between listening and hearing. Active listening means hearing with proper understanding of the message that is heard. By asking questions the speaker can ensure whether his/her message is understood or not by the receiver in the same terms as intended by the speaker.

Question 3.
(a) Give three differences between Shares and Debentures. [3]
(b) What is meant by supervision ? Explain three functions of a Supervisor. [4]
(c) Explain the importance of Delegation of Authority. [5]
Answer:
(a)

(b) Supervision is defined as guiding the activities of people w’m perform the work. It includes planning, organizing, directing and controlling the work and the activities of subordinates or employees.

Functions of a supervisor :
Planning and Organizing: Basic role of a supervisor is to plan the daily work schedule of the workers by guiding them the nature of their work and also dividing the work amongst the workers according to their interests, aptitudes, skills and interests.

Leadership and Guidance : A supervisor is the leader of workers working under him. He leads the workers and influences them to work their best. He also guides the workers by fixing production targets and by providing them instructions and guidelines to achieve those targets.

Motivation : A supervisor plays an important role by providing different incentives to workers to perform better. There are different inonetan and non-monetan incentives which can inspire the workers to work better and produce better.

(c) Delegation of authority means division of authority and powers downwards to the subordinate. Delegation is about entrusting someone else to do parts of your job. Delegation of authority can be defined as subdiv ision and sub-allocation of powers to the subordinates in order to achieve effective results.

Effective management: A manager passes routine work to his subordinates. He is free to concentrate on other important matters. The main job of a manager is to get the work done effectively. By delegating the authorities and responsibilities managers can get the work done effectively and efficiently from the subordinates.

Employees’ Development: As a result of delegation employees get more opportunities to utilize their talents. It allows them to develop those skills which help them to perform complex task. Delegation helps in making better future managers by giving them chance to use their skills, gain experience of work related to higher job position.

Motivation of employees: When the manager is sharing his responsibilities and authority with the subordinates it motivates the subordinates as they develop the feeling of belongingness and trust which is shown to them by their superiors. Some employees can be motivated by such kind of non-financial incentives.

Facilitates organizational growth : When the managers are passing their responsibility and authority to the subordinates they keep in mind the qualification and capability of all the subordinates. This leads to division of work and specialization which is very important for organizational growth.

Question 4.
(a) Explain any three disadvantages of issuing equity shares, from the Company s point of view.
(b) What is meant bv NEFT ? Give any two features of NEFT. [4|
(c) Explain five factors that should be taken into consideration while determining the price of a product or service.
Answer:
(a) 1. If only equity shares are issued, the company cannot take the advantage of trading on equity.

2. As equity’ capital cannot be redeemed, there is a danger of over capitalization.

3. Equity’ shareholders can put obstacles for management by manipulation and organizing themselves.

(b) NEFT stands for National Electronic Funds Transfer. This facility is provided by commercial banks to the persons requesting for sending funds from one branch of the bank to another branch of the same bank or different bank. The customer can transfer money from Rupee one to any limit at very’ nominal charges. These charges are much lesser than sending the funds through a draft.

(c) Cost of Production : Cost of production/service is the main component of price. No company can sell its product or sen ices at less than the cost of production. Before price fixation, it is necessary to compile data relating to the cost of production and keep that in mind.

Demand for Product: Intensiv e study of demand for product and sen ices in the market be undertaken before price fixation. If demand is relatively more than supply , higher price can be fixed.

Price of Competing Firms: It is necessary to take into consideration prices of the products of the competing firms before fixing the price. In case of cut-throat competition prices are required to be kept low.

Question 5.
(a) Explain any three objectives of Marketing. [ 3 ]
(b) What are Public Deposits ? Briefly explain any two merits of Public Deposits. [4 ]
(c) What is financial planning ? Explain three points of importance of financial planning for a business organisation. [ 5 ]Answer:
(a) Objectives of marketing are :
Creation of Demand : The first objective of marketing is to create demand through various means. An attempt is made to find out the preferences and tastes of the consumers. Goods and services are produced to satisfy the needs of the customers. Demand is also created by informing the customers the utility of various goods and serv ices.

Customer Satisfaction : The marketing manager must study the demands of customers before offering them any goods or services. Selling the goods or services is not that important as the satisfaction of the customers’ needs. Modern marketing is customer- oriented. It begins and ends with the customer.

Generation of profits : Marketing also targets at profits. If the firm is not earning profits, it will not be able to survive in the market. Moreover, profits are also needed for the growth and diversification of the firm.

(b) Public deposits refer to the unsecured deposits invited by companies from the public mainly to finance working capital needs. A company can invite public deposits for a period of six months to three years. Therefore, public deposits are primarily a source of short-term finance. However, the deposits can be renewed from time-to-time. Renewal facility enables companies to use public deposits as medium-term finance.

Merits of public deposits are :
Simplicity: Public deposits are a very convenient source of business finance. The company raising deposits has to simply give an advertisement and issue a receipt to each depositor

Economical: Interest paid on public deposits is lower than that paid on debentures and bank loans. Moreover, no underwriting commission, brokerage, etc. has to be paid. Interest paid on public deposits is tax deductible which reduces tax liability. Therefore, public deposits are a cheaper source of finance. .

(c) Financial planning helps you determine your short and long-term financial goals and create a
balanced plan to meet those goals.

Importance of financial planning :

• Financial planning provides policies and procedures for the sound administration of the finance function.
• Financial planning results in preparation of plans for the future. Thus, new projects could be undertaken smoothly.
• Financial planning ensures required funds from various sources for the smooth conduct of business.

Question 6.
(a) Explain any three points of importance of Planning. [3]
(b) Discuss any four features of Objectives, as a type of a Plan. [4]
(c) Explain the various steps involved in the process of Controlling, as a function of Management. [5]
Answer :
(a) Importance of planning :
Increases efficiency: Planning makes optimum utilization of all available resources. It helps to reduce wastage of valuable resources and avoids their duplication. It aims to give the highest returns at the lowest possible cost. Therefore, it increases the overall efficiency.

Reduces business-related risks: There are many risks involved in a business. Planning helps to forecast these business-related risks. It also helps to take the necessary precautions to avoid these risks and prepare for future uncertainties in advance. Therefore, it reduces business risks.

Facilitates proper coordination : The plans of all departments of an organization are well coordinated with each other. Similarly, the short-term, medium-term and long-term plans of an organization are also coordinated with each other. Such proper coordination is possible only because of efficient planning.

(b) Objectives should be framed for a single activity in mind. They should be result oriented. Objectives should not be v ague and they should be quantitative and measurable. Objectives must be achievable. They should not be unrealistic.

(c) Establishment of standards: Standards are benchmarks. Through standards, we can compare output to standardization. It serves the purpose of being a threshold which has to be achieved or surpassed. The creation and the prior establishment of standards is the first step involved in the process of controlling. The standards are established in accordance to the plan that is developed for the entire organization.

Ascertainment of output : The second main step in controlling is the measurement of performance. Gauging deviations from the planned measures is easier for measurable standards of performance as they can be quantified in units, cost, money terms, etc. However, non- measurable standards of performance are difficult to locate.

Identification of deviations : After the actual output is determined, it is compared and contrasted to the established standards. This step is central to the entire process of controlling as the deviations from the plan is identified during this step. Deviations can be referred to all those factors present in the actual output that prove distinct and different from the established standard.

Question 7.
(a) Distinguish between advertising and sales promotion. [3]
(b) Explain any four rights available to a consumer under the Consumer Protection Act. 1986. [4]
(c) What is meant by promotion mix ‘? Briefly explain the elements of promotion mix. [5]
Answer:
(a)

(b) Rights of consumers are :
Right to Safety : The Consumer Protection Act 1986 defines this right as a protection against goods and services that are hazardous to life and property. This particularly applies to medicines, pharmaceuticals, foodstuffs and automobiles. The right requires all such products of critical nature to life and property to be carefully tested and validated before being marketed to the consumer.

Right to Information : This right mentions the need for consumers to be informed about the quality and quantity of goods being sold. They must be informed about the price of the product and have access to other information specific to the product that they wish to consume.

Right to Choose: The consumer must have the right to choose between different products at competitive prices. This av oids monopoly in the market.

Right to Seek Redressal : When a consumer feels exploited, he/she has the right to approach a consumer court to file a complaint. A consumer court is a forum that hears the complaint and provides justice to the party that has been hurt. Thus, if the consumer feels he/she has been exploited, they can approach the court using this right.

(c) Promotion mix refers to the composure of several promotional tools used by the business to create, maintain and increase the demand for goods and services.

Elements of promotion mix :
Personal selling : It is a part of the promotional mix which involv es a one to one communication between buyers and customers (either potential or already customers). As it is a one-to-one communication, it generates direct contact with prospects and customers. Even though it is considered to be one of the most expensive forms of promotion, it is also considered to be the most successful as a seller-buy er relationship can be created and developed.

Advertising: One of the key factors in the promotional mix. which contributes to brand building and also how the market perceives the company, is advertising. It is always a big part of the promotional mix because of the far and wide reach of advertising and the message that you can send to your existing and potential customers. Good adv ertising can build a solid brand for the company. On the other hand, bad advertising with a wrong message, can cause the brand or product to fail.

Direct marketing: While advertising targets a mass-audience, direct marketing targets prospects and customers. Social media marketing, Email marketing, Internet marketing are all types of direct marketing used by companies. They have become important in the promotional mix lately because people are using internet far more than they used to a decade back. Companies employ direct marketing in order to engage in one-way communication with their customers, about product announcements, special promotions order confirmations as well as customer inquiries.

Sales promotions : Sales promotions are one of the most common types of promotion used by companies. Their main purpose is to stimulate purchasing and sales. While it has the potential of increasing sales, it is also beneficial for informing prospects about new products on the market or just to recapture old or lost customers. Such examples include: coupons, product samples, etc.

Question 8.
(a) Explain three features of goods, as an element of Product Mix. [3]
(b) Discuss any four types of preference shares. [4]
(c) State and explain the principles of management as laid down by F. W. Taylor. [5]
Answer:
(a) Features of Goods as an element of product mix

• Goods are one of the elements of marketing mix or program.
• Marketer can actualize its goals by producing, selling, improving and modifying the goods.
• Goods include tangible and non-tangible features or benefits.
• Goods are the medium to offer benefits and satisfaction to consumers.

(b) Types of preference shares :
Callable : The issuing company has the right to buy back these shares at a certain price on a certain date. Since the call option tends to cap the maximum price to which a preference share can appreciate (before the company buys it back), it tends to restrict stock price appreciation. Convertible : The owner of these preference shares has the option, but not the obligation, to convert the shares to a company’s common stock at some conversion ratio. This is a valuable feature w hen the market price of the common stock increases substantially, since the owners of preference shares can realize substantial gains by converting their shares.

Cumulative : If a company does not have the financial resources to pay a dividend to the owners of its preference shares, then it still has the payment liability’ and cannot pay dividends to its common shareholders for as long as that liability’ remains unpaid.

Non-cumulative : If a company does not pay a scheduled dividend, it does not have the obligation to pay the dividend at a later date. This clause is rarely used.

(c) Science, Not Rule of Thumb : In order to increase organizational efficiency, the Rule of Thumb’ method should be substituted by the methods developed through scientific analysis of work.

Rule of Thumb means decisions taken by manager as per their personal judgement’s. According to Taylor, even a small production activity can be scientifically planned. This will help in saving time as well as human energy. Decisions should be based on scientific enquiry with cause and effect relationships.

Harmony, Not Discord : Taylor emphasized that there should be complete harmony between the workers and the management since if there is any conflict between the two; it will not be beneficial either for the workers or the management Both the management and the workers should realize the importance of each other. In order to achieve this state, Taylor suggested complete mental revolution on the part of both management and workers.

It means that there should be complete change in the attitude and outlook of workers and management towards each other. It should always be kept in mind that prosperity for an employer cannot exist for a long time unless it is accompanied by the prosperity of the employees of that organization and vice versa.

Mental Revolution: The technique of Mental Revolution involves a change in the attitude of workers and management towards each other. Both should realize the importance of each other and should work with full cooperation. Management as well as the workers should aim to increase the profits of the organization.

Cooperation, Not Individualism : This principle is an extension of principle of “Harmony, not discord’ and lays stress on mutual cooperation between workers and the management. Cooperation, mutual confidence, sense of goodwill should prevail among both, managers as well as workers. The intention is to replace internal competition with cooperation.

Question 9.
Write short notes on the following :
(a) E.S.O.R [4]
(b) Features of Management as an art. [4]
(c) Channels of distribution [4]
Answer:
(a) ESOP (Employee stock ownership plan) refers to an employee benefit plan which offers employees an ownership interest in the organization. Employee stock ownership plans arc issued as direct stock, profit-sharing plans or bonuses and the employer has the sole discretion in deciding who could avail of these options.

However, Employee stock ownership plans are just options that could be purchased at a specified price before the exercise date. There are defined rules and regulations laid out in the Companies Rules which employers need to follow for granting of Employee stock ownership plans to their employees.

(b) Art implies application of know ledge and skill to trying about desired results. An art may be defined as personalized application of general theoretical principles for achieving best possible results. Art has the following characters :

Practical Knowledge : Every art requires practical knowledge therefore learning of theory is not sufficient. It is very important to know practical application of theoretical principles.

Personal Skill: Although theoretical base may be same for every artist, but each one has his own sty le and approach towards his job. That is why the level of success and quality of performance differs from one person to another.

Similarly management as an art is also personalized. Every manager has his own way of managing things based on his knowledge, experience and personality that is why some managers are known as good managers.

Creativity: Every artist has an element of creativity in line. That is why he aims at producing something that has never existed before which requires combination of intelligence and imagination. Management is also creative in nature like any other art. It combines human and non-human resources in useful way so as to achieve desired results. It tries to produce sw eet music by combining chords in an efficient manner.

Perfection through practice : Practice makes a man perfect. Every artist becomes more and more proficient through constant practice. Similarly managers learn through an art of trial and error initially but application of management principles over the years makes them perfect in the job of managing.

Result-Oriented : Even art is result oriented as it seeks to achieve concrete results. In the same manner, management is also directed towards accomplishment of pre-determined goals. Managers use various resources like men. money, material, machinery’ and methods to promote growth of an organization.

(c) Direct Channels : When the producer or the manufacturer directly sells the goods to the customers without involving any middlemen, it is known as direct channel. It is the simplest and the shortest mode of distribution. Selling through Indian Post. Internet or door to door selling etc. are the examples of this channel.
Methods of Direct Channel are :

• Door to door selling
• Internet selling
• Mail order selling
• Company owned retail outlets
• Telemarketing

Indirect Channels: When a manufacturer or a producer employs one or more middlemen to distribute goods, it is known as indirect channel.

Following are the main forms of indirect channels :
Manufacturer-Retailer-Consumer : This channel involves the use of one middleman i.e. retailer who in turn sells them to the ultimate customers. It is usually adopted for specialty goods. For example Tata sells its cars through company approved retailers.

Manufacturer-Wholesaler-Retailer-Customer : Under this channel, wholesaler and retailer act as a link between the manufacturer and the customer. This is the most commonly used channel for distributing goods like soap, rice, wheat, clothes etc.

Manufacturer-Agent-Wholesaler-Retailer-Consumer : This level comprises of three levels; middlemen (agent), wholesaler and the retailer. The manufacturers supply the goods to their agents w ho in turn supply them to wholesalers and retailers. This level is usually used when a manufacturer deals in limited products and even then wants to cover a wide market.

ISC Class 12 Commerce Previous Year Question Papers

ISC Biotechnology Year Question Paper 2010 Solved for Class 12

Maximum Marks: 80
Time allowed: Three hours

• Candidates are allowed additional 15 minutes for only reading the paper. They must NOT start writing during this time.
• Answer Question 1 (Compulsory) from Part I and five questions from Part II, choosing two questions from Section A, two questions from Section B and one question from either Section A or Section B.
• The intended marks for questions or parts of questions are given in brackets [ ].
• Transactions should be recorded in the answer book.
• All calculations should be shown clearly.
• All working, including rough work, should be done on the same page as, and adjacent to the rest of the answer.

Part-I
(Compulsory)

Question 1.
(a) Mention any one significant difference between each of the following : [5]
(i) Aldoses and ketoses
(ii) Pluripotent and multipotent cell
(iii) Chemostat and turbidostat
(iv) Codon and anticodon
(v) Androgenesis and gynogenesis.

(b) Answer the following questions : [5]
(i) What are nonsense codons
(ii) What is a micro processor ?
(iii) What is the role of oligonucleotide primer during DNA replication
(iv) Name two unique bases found in the tRNA structure.
(v) Who is regarded as the father of tissue culture technique ?

(c) Write the full form of the following: [5]
(i) NBPGR
(ii) VNTR
(iii) ARS
(iv) PEG
(v) ORF

(d) Explain briefly:
(i) Chargaff’s rule of equivalence
(ii) Database
(iii) Biolistic
(iv) Coenzyme
(v) Optical activity
Answer:
(a) Difference between
(i) Aldose : Aldose has one aldehyde molecule and has a double carbon and oxygen bond.
Ketose : Ketose has one ketone molecule and has the unique double carbon to carbon bond. Ketose also has no optical properties, which is one way that is being developed to detect blood sugar concentration.

(ii) Pluripotent stem cells : These are true stem cells, with the potential to make any differentiated cell in the body.

Multipotent stem cells: These are true stem cells but can only differentiate into a limited number of types. For example, the bone marrow contains multipotent stem cells that give rise to all the cells of the blood but not to other types of cells.

(in) Chemostat :A type of cell culture; a component of medium is in a growth limiting concentration; fresh medium is added at regular intervals and equal volume of culture is withdrawn.

Thrbidostat : A type of suspension culture; when culture reaches a predetermined cell density, a volume of culture is replaced by fresh medium; works well at growth rates close to the maximum.

(iv) Codon is the triplet sequence in the messenger RNA (mRNA) transcript which specifies a corresponding amino acid (or a start or stop command).

Anticodon is the corresponding triplet sequence on the transfer RNA (tRNA) which brings in the specific amino acid to the ribosome dining translation. The anticodon is complementary to the codon, that is, if the codon is AUU, then the anticodon is UAA.

(v) Androgenesis is development of an embryo from a fertilised irradiated egg, involving only the male nucleus.

Gynogenesis is development of a fertilised egg through the action of the egg nucleus, without participation of the sperm nucleus.

(b) (i) Nonsense codons : The three codons, UAA (known as ochre), UAG (amber) and UGA (opal), that do not code for an amino acid but act as signals for the termination of protein synthesis are known as nonsense codons.

(ii) Microprocessor : A microprocessor or processor is the heart of the computer and it performs all the computational tasks, calculations and data processing etc. inside the computer. Microprocessor is the brain of the computer. In the computers, the most popular type of the processor is the Intel Pentium chip and the Pentium IV is the latest chip by Intel Corporation. The microprocessors can be classified based on the following features.

Instruction Set: It is the set of the instructions that the Microprocessor can execute.

Bandwidth : The number of bits processed by the processor in a single instruction.

Clock Speed : Clock speed is measured in the MHz and it determines that how many instructions a processor can processed.

(iii) Oligonucleotides : Oligonucleotides composed of oligodeoxyribonucleotides (DNA) are often used in the polymerase chain reaction (PCR), a procedure that can amplify almost any small piece of DNA. There, the oligonucleotide is referred to as a primer, allowing DNA polymerase to extend the oligonucleotide and replicate the complementary strand.

(iv) Two unique bases are :
1. dihydrouridine(DHU)
2. pseudouridine

(v) Gottlieb Haberiandt

(c) Full forms of the followings:
(i) National Bureau Of Plant Genetic Resources
(ii) Variable Number Tandem Repeat
(iii) Agricultural Research Service
(iv) Polyethylene Glycol
(v) Open Reading Frame

(d) (i) Chargaff’s rule of equivalence : Deoxyribonucleic Acid (DNA), the genetic material is made up of four types of organic nitrogenous bases : adenine (A), guanine (G), thymine (T) and cytosine (C). Of these, A and G are the purines and T and C are the pyrimidines. Chargaff gave the base pairing rule or the rule of base equivalence which states that only one purine can combine with one pyrimidine. That means A can combine with T and G with C. Two purines or two pyrimidines cannot combine with each other; if they do so, there will be a sudden change in the characteristic of an organism. This sudden change is called mutation.

(ii) Database : A database is an organized collection of data for one or more multiple uses. One way of classifying databases involves the type of content, for example: bibliographic, full-text, numeric and image.

Biological databases are libraries of life sciences information, collected from scientific experiments, published literature, high-throughput experiment technology, and computational analysis. They contain information from research areas including genomics, proteomics, metabolomics, microarray gene expression, and phylogenetics. Information contained in biological databases includes gene function, structure, localization (both cellular and chromosomal), clinical effects of mutations as well as similarities of biological sequences and structures.

(iii) Biolistic : The particle gene gun is part of a method called the biolistic (also known as bioballistic) method, and under certain conditions, DNA (or RNA) become “sticky,” adhering to biologically inert particles such as metal atoms (usually tungsten or gold). By accelerating this DNA-particle complex in a partial vacuum and placing the target tissue (cells/nuclei) within the acceleration path, DNA is effectively introduced for genetic recombination.

(iv) Coenzyme : A non-proteinaceous organic substance that usually contains a vitamin or mineral and combines with a specific protein, the apoenzyme, to form an active enzyme system.

(v) Optical activity : The ability of some compounds to rotate the plane of polarized light because of the asymmetry of the molecule. If the plane of light is rotated to the right, the substance is dextrorotatory and is designated by the prefix (+); if laevorotatory (rotated to the left), the prefix is (-). A mixture of the two forms is optically inactive and is termed racemic.

Patr-II
(Answer any five Questions)

Question 2.
(a) What are lipids ? Explain the following properties of lipids: [4]
(i) Amphipathic nature
(ii) Saponification
(iii) Hydrogenation
(b) Mention the chief characteristics of embryonic stem cells. Give any two uses of such cells. [4]
(c) Write the names of any four important centres for biotechnology in India. [2]
Answer:
(a) Lipids: Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The main biological functions of lipids include energy storage, as structural components of cell membranes, and as important signaling molecules. Lipids are largely hydrocarbon like, and therefore do not dissolve in water but in non-polar solvents like diethyl ether and benzene.

Properties :
Amphipathic nature : Most membrane lipids are amphipathic, having a non-polar end and a polar end. The amphiphilic nature of some lipids allows them to form structures such as vesicles, liposomes, or membranes in an aqueous environment.

Saponification : The hydrolysis of triacylglycerol in the presence of sufficient sodium hydroxide is called saponification. The fatty acids are released as sodium salts and the mixture of these salts of long-chain fatty acids is soap.

Hydrogenation : Vegetable oils (liquids) are generally less expensive to produce than animal fats (solids). Using hydrogenation, chemists can break some of the carbon-carbon double bonds and replace them with hydrogen to make them chemically identical to the triacylglycerols in animal fats. Breaking one of the three double bonds in the molecule above can make the product melt above room temperature.

(b) Embryonic stem cells : are derived from embryos. Most embryonic stem cells are derived from embryos that develop from eggs that have been fertilized in vitro. The embryos from which human embryonic stem cells are derived are typically four or five days old and are a hollow microscopic ball of cells called the blastocyst. The blastocyst includes three structures: the trophoblast, which is the layer of cells that surrounds the blastocoel, a hollow cavity inside the blastocyst; and the inner cell mass, which is a group of cells at one end of the blastocoel that develop into the embry o proper.

Chief characteristics of stem cells : Embry onic stem cells differ from other kinds of cells in the body. Embryonic stem cells have three general properties:

1. they are capable of dividing and renewing themselves for long periods;
2. they are unspecialized; and
3. they can give rise to specialized cell types.

Embryonic stem cells are capable of dividing and renewing themselves for long periods. Unlike muscle cells, blood cells, or nerve cells-which do not normally replicate themselves- Embiyonic stem cells may replicate many times, or proliferate. Embryonic stem cells are unspecialized. One of the fundamental properties of a stem cell is that it does not have any tissue-specific structures that allow it to perform specialized functions. For example, a stem cell cannot work with its neighbors to pump blood through the body (like a heart muscle cell), and it cannot carry oxygen molecules through the bloodstream (like a red blood cell). Embryonic stem cells, can give rise to specialized cells, including heart muscle cells, blood cells, or nerve cells.

Uses of Embryonic stem cells: Studies of human embryonic stem cells will yield information about the complex events that occur during human development. A primary goal of this work is to identify how undifferentiated stem cells become the differentiated cells that form the tissues and organs.

Embryonic stem cells could also be used to test new drugs. For example, new medications could be tested for safety on differentiated cells generated from human pluripotent cell lines. Perhaps the most important potential application of human embryonic stem cells is the generation of cells and tissues that could be used for cell-based therapies.

(c) Important centres for Biotechnology in India :

• Department of Biotechnology (DBT)
• Center for Cellular & Molecular Biology (CCMB)
• Center for Biochemical Technology (CBT)
• National Institute of Immunology (Nil)

Question 3.
(a) How is DNA sequencing performed using Sangar’s dideoxy technique ? Give one limitation of this technique. [4]
(b) Write short notes on : [4]
(i) Shuttle vector
(ii) YAC
(iii) PCR
(iv) Electroporation
(c) Name any two industrial enzymes and give their uses. [2]
Answer:
(a) DNA sequencing: is the determination of the precise sequence of nucleotides in a sample of DNA.

Sanger dideoxy method : The most popular method for DNA sequencing is called the dideoxy method or Sanger method (named after its inventor, Frederick Sanger, who was awarded the 1980 Nobel prize in chemistry).

The Procedure : The DNA to be sequenced is prepared as a single strand.
This template DNA is supplied with

a mixture of all four normal (deoxy) nucleotides in ample quantities

• dATP
• dGTP
• dCTP
• dTTP

a mixture of all four dideoxynucleotides, each present in limiting quantities and each labeled with a ” tag

• that fluoresces a different color:
• ddATP
• ddGTP
• ddcTP
• ddTTP

DNA polymerase I

Because all four normal nucleotides are present, chain elongation proceeds normally until, by chance, DNA polymerase inserts a dideoxy nucleotide (shown as colored letters) instead of the normal deoxynucleotide (shown as vertical lines). If the ratio of normal nucleotide to the dideoxy versions is high enough, some DNA strands will succeed in adding several hundred nucleotides before insertion of the dideoxy version halts the process.

At the end of the incubation period, the fragments are separated by length from longest to shortest. The resolution is so good that a difference of one nucleotide is enough to separate that strand from the a different color when illuminated by a laser beam and an automatic scanner provides a next shorter and next longer strand. Each of the four dideoxynucleotides fluoresces
printout of the sequence.

Limitation : Limitations include non-specific binding of the primer to the DNA, affecting accurate read-out of the DNA sequence, and DNA secondary structures affecting the fidelity of the sequence.

(b) Short notes :
Shuttle vector : A shuttle vector is a vector (usually a plasmid) constructed so that it can propagate in two different host species. Therefore, DNA inserted into a shuttle vector can be tested or manipulated in two different cell types. The main advantage of these vectors is they can be manipulated in E. coli and then used in a system which is more difficult or slower to use (e.g., yeast, other bacteria).Shuttle vectors include plasmids that can propagate in eukaryotes and prokaryotes (e.g., both Saccharomyces cerevisiae and Escherichia coli) or in different species of bacteria (e.g., both E. coli and Rhodococcus erythropolis). There are also adenovirus shuttle vectors, which can propagate in E. coli and mammals. Shuttle vectors are frequently used to quickly make multiple copies of the gene in E. coli (amplification). They can also used for in vitro experiments and modifications (e.g., mutagenesis, PCR).

YAC : A yeast artificial chromosome (short YAC) is a vector used to clone large DNA fragments (larger than 100 kb and up to 3000 kb). It is an artificially constructed chromosome and contains the telomeric, centromeric, and replication origin sequences needed for replication and preservation in yeast cells. Built using an initial circular plasmid, they are linearised by using restriction enzymes, and then DNA ligase can add a sequence or gene of interest within the linear molecule by the use of cohesive ends. They were first described in 1983 by Murray and Szostak.

PCR : Polymerase chain reaction (PCR) is a technique to amplify a single or few copies of a piece of DNA across several orders of magnitude, generating thousands to millions of copies of a particular DNA sequence. The method relies on thermal cycling, consisting of cycles of repeated heating and cooling of the reaction for DNA melting and enzymatic replication of the DNA. Primers (short DNA fragments) containing sequences complementary to the target region along with a DNA polymerase (after which the method is named) are key components to enable selective and repeated amplification. As PCR progresses, the DNA generated is itself used as a template for replication, setting in motion a chain reaction in which the DNA template is exponentially amplified. PCR can be extensively modified to perform a wide array of genetic manipulations.

Electroporation : Electroporation, or electropermeabilization, is a significant increase in the electrical conductivity and permeability of the cell plasma membrane caused by an externally applied electrical field. It is usually used in molecular biology as a way of introducing some substance into a cell, such as loading it with a molecular probe, a drug that can change the cell’s function, or a piece of coding DNA.

Electroporation is a dynamic phenomenon that depends on the local transmembrane voltage at each cell membrane point. It is generally accepted that for a given pulse duration and shape, a specific transmembrane voltage threshold exists for the manifestation of the electroporation phenomenon (from 0.5 V to 1 v). This leads to the definition of an electric field magnitude threshold for electroporation (E_th). That is, only the cells within areas where E E_th are electroporated. If a second threshold (E_th) is reached or surpassed, electroporation will compromise the viability of the cells, i.e.. irreversible electroporation.

(c) Two industrial enzymes with uses :
Amylases (from fungi and plants) : Production of sugars from starch, such as in making high-fructose com syrup.
Rennin (derived from the stomachs of young ruminant animals) : Manufacture of cheese, used to hydrolyze protein.

Question 4.
(a) Explain any one biochemical technique based on each of the following principles : [4]
(i) Sedimentation coefficient
(ii) Polarity
(b) What are the steps involved in the construction of an rDNA molecule for the purpose of gene cloning ? [4]
(c) How is distant hybridization technique useful in plant tissue culture ? [2]
Answer:
(a) Biochemical techniques based on
(i) Sedimentation coefficient : The sedimentation coefficient s of a particle is used to characterize its behaviour in sedimentation processes, notably centrifugation. It is defined as the ratio of a particle’s sedimentation velocity to the acceleration that is applied to it (causing the sedimentation).
\(s=\frac{v_{t}}{a}\)

Sedimentation: In a sedimentation experiment, the applied force accelerates the particles to a terminal velocity v_term at which the applied force is exactly canceled by an opposing drag force. For small enough particles (low Reynolds number), the drag force varies linearly with the terminal velocity, i.e., F_drag = fv_term (Stokes flow) where f depends only on the properties of the particle and the surrounding fluid. Similarly, the applied force generally varies linearly with some coupling constant (denoted here as q) that depends only on the properties of the particle, F_app = qE_app Hence, it is generally possible to define a sedimentation coefficient S^def = q/f that depends only on the properties of the particle and the surrounding fluid. Thus, measuring s can reveal underlying properties of the particle.

Rate zonal centrifugation : This is a type of density gradient centrifugation. The sample is applied in a thin zone at the top of the centrifuge tube. Under centrifugal force, the particles will sediment through the gradient in separate zones based on their sedimentation coefficient or‘S’value.

(ii) Technique used to separate biomolecules based on polarity :
Ion-exchange chromatography: It is defined as the reversible exchange of ions in solution with ions electrostatically bound to some sort of insoluble support medium. Separation is obtained since different molecules have different degree of interaction with the ion- exchanger due to difference in their charges, charge densities and distribution of charge on their surfaces. These interactions can be controlled by varying conditions such as ionic strength and PH.

An ion-exchanger consists of an insoluble matrix to which charged groups have been covalently bound. Ion exchange separations are carried out mainly in columns packed with an ion-exchanger. There are two types of ion-exchanger, namely cation and anion exchangers. Cation exchangers possess negatively charged groups and these will attract positively charged cations. Anion exchangers have positively charged groups that will attract negatively charged anions. After the ion exchange the molecules can be eluted from the matrix by selective desorption. The selective desorption can be achieved by changes in PH and /or ionic concentration or by affinity elution, in which case an ion that has greater affinity for the exchange than has the bound ion is introduced into the system.

(b) Recombinant DNA (rDNA) : It is a form of DNA that does not exist naturally, which is created by combining DNA sequences that would not normally occur together. In terms of genetic modification, recombinant DNA is introduced through the addition of relevant DNA into an existing organismal DNA, such as the plasmids of bacteria, to code for or alter different traits for a specific purpose, such as antibiotic resistance. Recombinant DNA is DNA that has been created artificially. DNA from two or more sources is incorporated into a single recombinant molecule.

• Treat DNA from both sources with the same restriction endonuclease (BamHI in this case).
• BamHI cuts the same site on both molecules
• 5′ GGATCC 3′
• 3’CCTAGG5′
• The ends of the cut have an overhanging piece of single-stranded DNA.
• These are called “sticky ends” because they are able to base pair with any DNA molecule containing the complementary sticky end.
• In this case, both DNA preparations have complementary sticky ends and thus can pair with each other when mixed.
• DNA ligase covalently links the two into a molecule of recombinant DNA.

To be useful, the recombinant molecule must be replicated many times to provide material for analysis, sequencing, etc., Producing many identical copies of the same recombinant molecule is called cloning. Cloning can be done in vitro, by a process called the polymerase chain reaction (PCR). Here, however, we shall examine how cloning is done in vivo. Cloning in vivo can be done in :

• unicellular microbes like E. coli
• unicellular Eukaryotas like yeast and
• Mammalian cells grown in tissue culture.

In every case, the recombinant DNA must be taken up by the cell in a form in which it can be replicated and expressed. This is achieved by incorporating the DNA in a vector. A number of viruses (both bacterial and of mammalian cells) can serve as vectors. But here let us examine an example of cloning using E. coli as the host and a plasmid as the vector.

(c) Distant hybridization : It implies crosses of species, subspecies, breeds and strains for the purpose of obtaining marketable hybrids of the first generation.

Importance of distant hybridization:

• Distant hybridization is a combination of valuable features of parental forms in hybrids without noticeable increase in viability and, with intermediate growth rate.
• They comprise both heterosis hybrids and hybrid forms with a favorable combination of parental features.
•  Abortion of embryos at one or the other stage of development is a characteristic feature of distant hybridization, e.g., the crossing of two species or varieties often fails when using distant parents who do not share many chromosomes. Embryo rescue is the process when plant breeders rescue inherently weak, immature or hybrid embryos to prevent degeneration. Common in lily, hybridizing to create new interspecific hybrids between the various lily groups (such as Asiatic, Oriental, Trumpet, etc ).

Question 5.
(a) Discuss the Cell Culture technology under the following headings [4]
(i) Different types of nutrient media used.
(ii) Sterilization of instruments and transfer area.
(b) What is a DNA library ? How is a genomic DNA library formed ? [4]
(c) Give two applications of somatic hybridization. [2]
Answer: .
(a) (i) Nutrient media : It is a source of amino acids and nitrogen (e.g., beef, yeast extract). This is an undefined medium because the amino acid source contains a variety of compounds with the exact composition being unknown. Nutrient media contain all the elements that most bacteria need for growth and are non-selective, so they are used for the general cultivation and maintenance of bacteria kept in laboratory culture collections. An undefined medium (also known as a basal or complex medium) is a medium that contains :

• a carbon source such as glucose for bacterial growth
• water
• various salts needed for bacterial growth

Defined media (also known as chemically defined media or synthetic media)

• all the chemicals used are known
• does not contain any yeast, animal or plant tissue

Differential medium

• some sort of indicator, typically a dye, is added, that allows for the differentiation of particular chemical reactions occurring during growth.

(ii) Sterlization of instruments : The metallic instruments (e.g., forceps, scalpels,needles,spatula etc.) are flame sterilized i.e., dipping them in 75% ethanol followed by flaming and cooling. It is called incineration.

Sterlization of transfer area : Floor and walls of culture room are first washed with detergent and then 2% sodium hypochlorite or 95% ethanol. Larger surface area is sterilized by exposure to UV light.

(b) DNA Library: DNA library is a collection of DNA fragments of one organism, each carried by a plasmid or virus and cloned in an appropriate host. A DNA probe is used to locate a specific DNA sequence in the library. A collection representing the entire genome is called a genomic (DNA) library. An assortment of DNA copies of messenger RNA produced by a cell is known as a complimentary DNA (cDNA) library.

Construction of Genomic Library: The process of subdividing genomic DNA into clonable elements and inserting them into host cells is called creating a library.

A complete library, by definition, contains the entire genomic DNA of the source organism and is called as genomic library. A genomic library is a set of cloned fragments of genomic DNA. The process of creating a genomic library includes four steps :

In the first step the high molecular weight genomic DNA is separated and subjected to restriction enzyme digestion by using two compatible restriction enzymes.

In the second step, the fragments are then fractionated or separated by using agarose gel electrophoresis to obtain fragments of required size.

These fragments are then subjected to alkaline phosphatase treatment to remove the phosphate. In the third step, the dephosphorylated insert is ligated into vector which could be a plasmid, phage or cosmid, depending upon the interest of the researcher.

In the last step, the recombinant vector is introduced into the host by electroporation and amplified in host. In principle, all the DNA from the source organism is inserted into the host, but this is not fully possible as some DNA sequences escape the cloning procedure. Genomic library is a source of genes, and DNA sequences. A genomic library is a set of cloned fragments of genomic DNA. Prior information about the genome is not required for library construction for most organisms. In principle, the genomic DNA, after the isolation, is subjected to RE enzyme for digestion to generate inserts.

(c) Application of Somatic Hybridization :

• Somatic cell fusion appears to be the only means through which two different parental genomes can be recombined among plants that cannot reproduce sexually (asexual or sterile).
• Protoplasts of sexually sterile (haploid, triploid, and aneuploid) plants can be fused to produce fertile diploids and polyploids.
• Somatic cell fusion overcomes sexual incompatibility barriers. In some cases somatic hybrids between two incompatible plants have also found application in industry or agriculture.
• Somatic cell fusion is useful in the study of cytoplasmic genes and their activities and this information can be applied in plant-breeding experiments.

Question 6.
(a) Explain the post-transcriptional changes in mRNA and tRNA of a eukaryotic cell. [4]
(b) Classify proteins on the basis of their functions. Also give an example of each type. [4]
(c) Mention any two significant applications of bioinformatics. [2]
Answer:
(a) Post-transcriptional changes in mRN A and tRNA
RNA transcripts in eukaryotes are modified, or processed, before leaving the nucleus to yield functional mRNA.

Eukaryotic RNA transcripts can be processed in two ways:

1. Covalent alteration of both the 3′ and 5′ ends.
2. Removal of intervening sequences.

The pre-mRNA (primary transcript that will be processed to functional mRNA) molecule undergoes three main modifications. These modifications are 5′ capping, 3′ polyadenylation, and RNA splicing, which occur in the cell nucleus before the RNA is translated.

5’Capping:
Capping of the pre-mRNA involves the addition of 7-methylguanosine (m7G) to the 5′ end. In order to achieve this, the terminal 5′ phosphate requires removal, which is done by the aid of a phosphatase enzyme. The enzyme guanosyl transferase then catalyses the reaction which produces the diphosphate 5′ end. The diphosphate 5′ prime end then attacks the a phosphorus atom of a GTP molecule in order to add the guanine residue in a 5’5′ triphosphate link. The enzyme S-adenosyl methionine then methylates the guanine ring at the N-7 position.

This type of cap, with just the (m7G) in position is called a cap 0 structure. The ribose of the adjacent nucleotide may also be methylated to give a cap 1. Methylation of nucleotides downstream of the RNA molecule produce cap 2, cap 3 structures and so on. In these cases the methyl groups are added to the 2′ OH groups of the ribose sugar. The cap protects the 5′ end of the primary RNA transcript from attack by ribonucleases that have specificity to the 3’5′ phosphodiester bonds.

Cleavage and Polyadenylation :
The pre-mRNA processing at the 3′ end of the RNA molecule involves cleavage of its 3′ end and then the addition of about 200 adenine residues to form a poly(A) tail. The cleavage and adenylation reactions occur if a polyadenylation signal sequence (5′- AAU AAA-3′) is located near the 3′ end of the pre-mRNA molecule, which is followed by another sequence, which is usually (5′-CA-3′). Poly(A) polymerase then adds about 200 adenine units to the new 3′ end of the RNA molecule using ATP as a precursor. As the poly(A) tails is synthesised, it binds multiple copies of poly(A) binding protein, which protects the 3’end from ribonuclease digestion.

mRNA Splicing:
RNA splicing is the process by which introns, regions of RNA that do not code for protein, are removed from the pre-mRNA and the remaining exons connected to re-form a single continuous molecule. Although most RNA splicing occurs after the complete synthesis and end-capping of the pre-mRNA, transcripts with many exons can be spliced co-transcriptionally. The splicing reaction is catalyzed by a large protein complex called the spliceosome assembled from proteins and small nuclear RNA molecules that recognize splice sites in the pre-mRNA sequence.RNA

tRNA Splicing:
tRNA splicing is another rare form of splicing that usually occurs in tRNA. The splicing reaction involves a different biochemistry than the spliceomsomal and self-splicing pathways. Ribonucleases cleave the RNA and ligases join the exons together. This form of splicing does also not require any RNA components for catalysis. In biochemistry, a ligase is an enzyme that can catalyse the joining of two molecules (ligation or glue together) by forming a new chemical bond, with concomitant hydrolysis of ATP or other similar molecules.

Most of higher eukaryotic genes coding for mRNA, tRNA and some coding for rRNA are interrupted by unrelated regions called introns. The other parts of the genes are called exons. Exons contain information that appears in the functional mRNA.
Genes for mRNA have 0 to 60 introns.
Genes for tRNA have 0 to 1 intron.

(b) Classification of proteins based on their functions
Proteins are responsible for many different functions in the living cell. Classification of proteins on the basis of functions is as follows :

Enzymes : Proteins that catalyze chemical and biochemical reactions within living cell and outside. This group of proteins probably is the biggest and most important group of the proteins. Enzymes are responsible for all metabolic reactions in the living cells. Well known and very interesting examples are : DNA and RNA-polymerases, dehydrogenases etc.

Hormones: Proteins that are responsible for the regulation of many processes in organisms. Hormones are usually quite small and can be classifies as peptides. Most known protein hormones are : insulin, growth factor, lipotropin, prolactin etc. Many protein hormones are predecessor of peptide hormones, such as endorfme, enkephalin etc. It is possible to increase this group of proteins by adding of all protein venoms.

Transport proteins : These proteins are transporting or store some other chemical compounds and ions. Some of them are well known : cytochrome C-electron transport; haemoglobin and myoglobin – oxygen transport; albumin – fatty acid transport in the blood stream etc. It is possible to classify trans membrane protein channels as transport proteins as well.

Immunoglobulin or Antibodies : Proteins that are involved in the immune response of the organism to neutralize large foreign molecules, which can be a part of an infection. Sometimes antibodies can act as enzymes. Sometimes this group of proteins is considered as a bigger group of protective proteins with adding such proteins as lymphocyte antigen¬recognizing receptors, antiviral agents such as interferon, tumor necrosis factor (TNF). Probably the clotting of blood proteins, such as fibrin and thrombin should be classified as protective proteins as well.

Structural proteins : These proteins are maintaining structures of other biological components, like cells and tissues. Collagen, elastin, a-keratin, sklerotin, fibroin – these proteins are involved into formation of the whole organism body. Bacterial proteoglycans and virus coating proteins also belongs to this group of proteins. Currently we do not know about other functions of these proteins.

Motor proteins : These proteins can convert chemical energy into mechanical energy. Actin and myosin are responsible for muscular motion. Sometimes it is difficult to make a strict separation between structural and motion proteins.

Receptors : These proteins are responsible for signal detection and translation into other type of signals. Sometimes these proteins are active only in complex with low molecular weight compounds. Very well known member of this protein family idopsin/rhodopsin – light detecting protein. Many receptors are transmembrane proteins.

Signalling proteins: This group of proteins is involved into signalling translation process. Usually they significantly change conformation in presence of some signalling molecules. These proteins can act as enzymes. Other proteins, usually small, can interact with receptors. Classical example of this group of proteins is GTPases.

Storage proteins: These proteins contain energy, which can be released during metabolism processes in the organism. Egg ovalbumin and milk casein are such proteins. Almost all proteins can be digested and used as a source of energy and building material by other organisms.

(c) Two significant functions of Bioinformatics :
The biological information hidden in DNA / RNA and protein sequences are processed into genes and proteins and a relationship is established between a gene and protein by bioinformatics tools.

Using bioinformatics tools such as Genmark (for bacteria) and GenScan (for eukaryotes) gene prediction is carried out in organisms. GenScan can identify introns, exons, promoter sites and polyA signals and other gene identification algorithms.

Question 7.
(a) Discuss the applications of plant tissue culture emphasizing its role in obtaining :
(i) Stress-tolerant plants
(ii) Biodegradable plastic
(b) Briefly explain the principle and application of the technique – Southern blotting similar technique for protein identification.
(c) What is DNA Micro-array technology’ ?
Answer:
(a) (i) Stress-tolerant plants : Plant tissue culture develop ways of making plants better suited to site-related, environmental challenges like drought, salinity or extreme temperatures. With agriculture being relegated to marginal land and with the prospect of climate change induced drought, these traits are considered crucial ways of securing the world’s food supply.

Researchers have been able to identify several plant genes that are involved with stress tolerance. Some of these genes code for antioxidants, enzymes that modify lipids in the cell membrane, stress-response transcription factors, proteins that maintain ion homeostasis, heat shock proteins, or enzymes that synthesis important stress-response compounds. Some of these factors have been used to produce transgenic plants with increased stress tolerance.

Drought tolerance : Water is crucial for all living things. Plants use water as a solvent, a transport medium, an evaporative coolant, physical support, and as a major ingredient for photosynthesis. Without sufficient water, agriculture is impossible. Therefore, drought tolerance is an extremely important agricultural trait.

One way of engineering drought tolerance is by taking genes from plants that are naturally drought tolerant and introducing them to crops. The ressurection plant (.Xerophyta viscosa), a native of dry regions of southernmost Africa, possesses a gene for a unique protein in its cell membrane. Experiments have shown that plants given this gene are less prone to stress from drought and excess salinity.

Some genes have been found that control the production of the thin, protective cuticle found on leaves. If crops can be grown with a thickened waxy cuticle, they could be better equipped for dealing with dryness.

Salt tolerance : Irrigation has enabled the transformation of arid regions into some of the world’s most productive agricultural areas. Excess salinity, however, is becoming a major problem for agriculture in dry parts of the world. In several cases, scientists have used biotechnology to develop plants with enhanced tolerance to salty conditions.

Researchers have noticed that plants with high tolerance to salt stress possess naturally high levels of a substance called glycine betaine. Further, plants with intermediate levels of salinity tolerance have intermediate levels, and plants with poor tolerance to salinity have little or none at all. Genetically modified tomatoes with enhanced glycinebetaine production have increased tolerance to salty conditions.

Another approach to engineering salt tolerance uses a protein that takes excess sodium and diverts it into a cellular compartment where it does not harm the cell. In the lab, this strategy was used to create test plants that were able to flower and produce seeds under extreme salt levels. Commercially available crops with such a modification are still several years away.

(ii) Biodegradable Plastics : PTC is currently employed in the synthesis of plastic which is biodegradable i.e., unlike other plastics; this plastic can be broken down into simpler substances by microorganisms.

The biodegradable plastic is made from lactic acid which is produced at the time of bacterial fermentation of plant materials like discarded stalks of com. In the process, molecules of lactic Acid are chemically grouped to form the biodegradable plastic. In fact, the biodegradable plastic is a material which has most of the properties of plastic except the property of being non – biodegradable. The biodegradable plastic polyhydroxyalkanates for e.g., polyhydroxylbutyrate (PHB) are obtained commercially by fermentation with bacterium Alcaligenes eutrophus. The genetically engineered Arabidopsis plants produced polyhydroxylbutyrate (PHB) globules in their chloroplasts without effecting plant growth and development. The large scale of polyhydroxylbutyrate (PHB) can be extracted from leaves as well as from transgenic plants.

(b) Principle of Southern blotting: In this technique, DNA is usually converted into conveniently sized fragments by restriction digestion. The fragments are then separated by migration through an agarose gel, and transferred to a nylon or nitrocellulose membrane by capillary action. The DNA of interest can be identified by hybridization to radioactive or chemiluminescent probes and visualized by autoradiography or staining.

Application of Southern blotting:

• Southern blots can easily provide a physical map of restriction sites within a gene located normally on a chromosomes.
• Southern blots reveal the number of copies of the gene in a genome.
• The degree of similarity of the gene when compared with other complementary genes. Western blotting is the technique for protein identification.

(c) DNA microarray : A DNA microarray is a multiplex technology used in molecular biology and in medicine. It consists of an arrayed series of thousands of microscopic spots of DNA oligonucleotides, each containing picomoles (10-12 moles) of a specific DNA sequence, known as probes. This can be a short section of a gene or other DNA element that are used to hybridize a cDNA or cRNA sample (called target) under high-stringenev conditions. Probe- target hybridization is usually detected and quantified by detection of fluorophore-, silver-, or chemiluminescence-labeled targets to determine relative abundance of nucleic acid sequences in the target. Since an array can contain tens of thousands of probes, a microarray experiment can accomplish many genetic tests in parallel. Therefore arrays have dramatically accelerated many types of investigations.

Question 8.
(a) Give four differences between an inducible and a repressible operon. [4]
(b) Discuss the impact of the following factors on enzyme activity’: [4]
(i) Substrate concentration
(ii) Temperature
(iii) Presence of a competitive inhibitor
(iv) Enzyme concentration
(c) Name any two disaccharides and give their structural units.
Answer:
(a) Differences between Inducible and Repressible Operon

 (b) Factors Affecting Enzyme Activity:
(i) Substrate concentration: It depends on the type of enzyme reaction. For a competitive enzyme reaction, the increase in substrate concentration can have an inverse effect on the activity, but for a normal enzyme reaction, as long as the substrate concentration isn’t saturated, in general it will increase activity. At lower concentrations, the active sites on most of the enzyme molecules are not filled because there is not much substrate. Higher concentrations cause more collisions between the molecules. With more molecules and collisions, enzymes are more likely to encounter molecules of reactant.

The maximum velocity’ of a reaction is reached when the active sites are almost continuously filled. Increased substrate concentration after this point will not increase the rate. Reaction rate therefore increases as substrate concentration is increased but it levels off.

(ii) Temperature : Higher temperature generally causes more collisions among the molecules and therefore increases the rate of a reaction. More collisions increase the likelihood that substrate will collide with the active site of the enzyme, thus increasing the rate of an enzyme-catalyzed reaction. Above a certain temperature, activity begins to decline because the enzyme begins to denature. The rate of chemical reactions therefore increases with temperature but then decreases as enzymes denature.

(iii) Presence of Competitive inhibitor: A competitive inhibitor is any compound which closely resembles the chemical structure and molecular geometry of the substrate. The inhibitor competes for the same active site as the substrate molecule. The inhibitor may interact with the enzyme at the active site, but no reaction takes place. The inhibitor is “stuck” on the enzyme and prevents any substrate molecules from reacting with the enzyme. However, a competitive inhibition is usually reversible if sufficient substrate molecules are available to ultimately displace the inhibitor. Therefore, the amount of enzyme inhibition depends upon the inhibitor concentration, substrate concentration, and the relative affinities of the inhibitor and substrate for the active site.

(iv) Enzyme Concentration: If there is insufficient enzyme present, the reaction will not proceed as fast as it otherwise would because all of the active sites are occupied with the reaction. Additional active sites could speed up the reaction. As the amount of enzyme is increased, the rate of reaction increases. This is so because when more enzyme molecules are present, more substrate molecules can be acted upon at the same time. This means that the total substrate molecules are broken down quickly. If there are more enzyme molecules than are needed, adding additional enzyme will not increase the rate. Reaction rate therefore increases as enzyme concentration increases but then it levels off.

(c) Disaccharides with their structural units

Question 9.
(a) Explain the following methods of selection of recombinant cell : [4]
(i) Insertional inactivation
(ii) Blue-white selection
(b) Differentiate between : [4]
(i) Local and global sequence alignment
(ii) RAM and ROM
(c) Name any two protein databases and two genomic databases. [2]
Answer:
(a) (i) Insertional inactivation: Harder problem to solve is to determine w hich of the transformed colonies comprise cells that contain recombinant DNA molecules, and which contain self-ligated vector molecules. Insertional inactivation is the inactivation of a gene by inserting a fragment of DNA into the middle of its coding sequence. Any future products from the inactivated gene will not work because of the extra codes added to it. Recombinants can therefore be identified because the characteristic coded by the inactivated gene is no longer visible.

pBR322 contains genes which code for ampicillin resistance and tetracycline resistance. BamHI cuts in the middle of the gene which codes for tetracycline resistance. If a gene is inserted here, the plasmid loses it ability to code for tetracycline resistance. Thus the plasmid containing the recombinant gene is resistant to ampicillin but sensitive to tetracycline. To screen, we use replica plates.

The pUC8. plasmid is ampicillin resistant and contains a gene lac Z’ which partially codes for β galactosidase. To make the plasmid capable of coding for the whole protein, we add the missing DNA along with the recombinant gene. The host which contains the plasmid pUC8 is resistant to ampicillin and is also capable of producing p galactosidase.

(ii) The blue-white screen is a molecular technique that allows for the detection of successful ligations in vector-based gene cloning. DNA of interest is ligated into a vector. The vector is then transformed into competent cell (bacteria). In this method a reporter gene lac Z is inserted in the vector. The lac Z encodes for the enzyme b- galactosidase which breaks a synthetic substrate X-gal (5-bromo-4-chloro-indolyl-b-D-galacto-pyranoside) into insoluble blue colored product. The competent cells are grown in the presence of X-gal. If the ligation was successful, the bacterial colony will be white because b- galactosidase is not synthesized due to the inactivation of lac Z; if not, the colony will be blue. This technique allows for the quick and easy detection of successful ligation, without the need to individually test each colony. An example of such a vector is the artificially reconstructed plasmid pUC19.

(b) (i) Global Vs local alignments : Illustration of global and local alignments demonstrating the ‘gappy’ quality of global alignments that can occur if sequences are insufficiently similar

Global alignments, which attempt to align every residue in every sequence, are most useful when the sequences in the query7 set are similar and of roughly equal size (This . does not mean global alignments cannot end in gaps). A general global alignment technique is the Needleman-Wunsch algorithm, which is based on dynamic programming. Local alignments are more useful for dissimilar sequences that are suspected to contain regions of similarity or similar sequence motifs within their larger sequence context. The Smith-Waterman algorithm is a general local alignment method also based on dynamic programming. With sufficiently similar sequences, there is no difference between local and global alignments.

(ii) ROM :

• ROM is a Read only Memory.
• The contents of Rom can only be read.
• One cannot modify or write the contents of ROM.
• It is transistor based.
• It is non volatile.
• It is costly.
• Information stored in ROM is very important for computer system to work properly.

RAM :

• RAM stands for Random Access Memory.
• It is a read/write memory.
• It is capacitive based.
• It is volatile.
• It is cheaper than ROM.
• Information stored in RAM is mainly user based and has little or no link with the internal working of computer.

(c) Protein Databases :

Genome Databases :
Saccharomyces Genome Database (SGD) : Is a scientific database of the molecular biolog) and genetics of the yeast Saccharomyces cerevisiae, which is commonly known as baker s or budding yeast.

The Integrated Microbial Genomes (IMG): Serves as a community resource for comparative analysis and annotation of all publicly available genomes from three domains of bioinformatics

ISC Class 12 Biotechnology Previous Year Question Papers

ISC Biotechnology Previous Year Question Paper 2011 Solved for Class 12

Maximum Marks: 80
Time allowed: Three hours

• Candidates are allowed additional 15 minutes for only reading the paper. They must NOT start writing during this time.
• Answer Question 1 (Compulsory) from Part I and five questions from Part II, choosing two questions from Section A, two questions from Section B and one question from either Section A or Section B.
• The intended marks for questions or parts of questions are given in brackets [ ].
• Transactions should be recorded in the answer book.
• All calculations should be shown clearly.
• All working, including rough work, should be done on the same page as, and adjacent to the rest of the answer.

Part-I
(Compulsory)

Question 1
(a) Mention any one significant difference between each of the following : [5]
(i) Nucleotide and nucleoside.
(ii) Plasmids and phages.
(iii) Fluorescence spectrometry and mass spectrometry.
(iv) Primer and primases.
(v) Introns and exons.

(b) Answer the following questions : [5]
(i) What are oil eating bacteria?
(ii) What are single cell proteins?
(iii) Who proposed the Operon concept of gene regulation?
(iv) Explain the term transposons.
(v) Name one polysaccharide found in the cell wall of bacteria and one polysaccharide found in fungi.

(c) Write the full form of the following: [5]
(i) NCBI
(ii) EST
(iii) ROM
(iv) PACE
(v) FMN

(d) Explain briefly: [5]
(i) RNA dependent DNA polymerase
(ii) EMBL
(iii) Isoelectric focussing
(iv) Cosmids
(v) Vitamins
Answer:
(a) (i) Nucleotide: The nucleotide is a condensation product of heterocyclic nitrogen base, a pentose sugar like ribose or deoxyribose, and a phosphate or polyphosphate group.

Nucleoside: Nucleoside consisting of a pentose sugar, usually ribose or deoxyribose, and a nitrogen base-purine or pyrimidine.

(ii) Plasmids: Plasmids are the extra-chromosomal, independent, self replicating, circular, double stranded DNA molecules naturally found in all bacteria and some fungi.

Phages: Bacteriophage (i.e., viruses that infect bacteria) are obligate intracellular parasites that multiply inside bacteria by making use of some or all of the host biosynthetic machinery.

(iii) Fluorescence Spectrometry: Fluorescence spectrophotometry is a technique that assay the state of a biological system by studying the absorption spectra of different radiations and its interactions with fluorescent probe molecules.

Mass Spectrometry: Mass spectrometry (MS) is an analytical technique that involves separation of ions of different mass and energy when fixed magnetic and electric fields are employed.

(iv) Primer: A primer is a short strand of RNA that serves as a starting point for DNA synthesis They are required for DNA replication because DNA polymerases can only add new nucleotides to an existing strand of DNA.

Primases: Primase is an enzyme that catalyzes the synthesis of a short RNA segment (called a primer) complementary to a ssDNA template.

(v) Introns: Introns are non-coding DNA base sequences , which are found between exons, but are not transcribed part of mature mRNA.

Exons: Exons are coding DNA base sequences that are transcribed into wzRNA and finally code for amino acids in the proteins.

(b) (i) Bacteria that decompose and use oil as their source of energy are called as oil eating bacteria e.g., Pseudomonasputida, P.capacia etc. are efficient degraders created through genetic engineering. They need to be established in environment. They (“the oil-eating bacteria”) could digest about two- thirds of the hydrocarbons that would be found in a typical oil spill.

(ii) The term single cell protein (SCP) refers to biomass of dry cells of microorganisms such as yeast, bacteria, mushroom (fungi) and algae which grow on different carbon sources. The name “single cell protein” was used for the first time by the M.I.T. Professor Carol Wilson.

(iii) Jacob and Monod proposed the Operon concept of Gene Expression in bacteria.

(iv) Transposons : Transposons are sequences of DNA that can move around to different positions within the genome of a single cell. Transposons are called “Jumping genes”, and are examples of mobile genetic elements.
Two types of Transposons are possible :

• Retrotrahsposons and
• DNA transposons.

In this process, they may :

• cause mutations
• increase (or decrease) the amount of DNA in the genome.

(v) Peptidoglycans (mucopeptides, glycopeptides, mureins) are the structural elements of bacterial cell walls. Fungi possess cell walls made-up of chitin, polymer of glucosamine,

(c) (i) NCBI: National Centre for Biotechnology Information

(ii) EST : Expressed sequenced tag

(iii) ROM : Read only memory

(iv) PAGE : Polyacrylamide gel electrophoresis

(v) FMN : Flavin mononucleotides.

(d) (i) RNA-dependent DNA polymerase enzyme is used for the synthesis of a complementary DNA strand from RNA molecule as a template. It is produced by HTV and other retroviruses which help them to synthesize DNA from their viral RNA.

(iii) Isoelectric focusing (IEF), also known as electrofocusing, is a technique for separating different molecules by their electric charge differences. It is a type of zone electrophoresis, usually performed on proteins in a gel.

(iv) Cosmids are constructed by uniting some part of the bacterial plasmids with a ‘ori’ gene, an antibiotic selection marker and a cloning site with one or more recently two ‘cos’ sites derived from bacteriophage lambda.

(v) A vitamin is an organic compound required as a nutrient in very small amounts by an organism. They act as co-factor of an enzyme. It cannot be synthesized in sufficient quantities by an organism, and must be obtained from the diet.

Part-II
(Answer any five questions)

Question 2.
(a) Mention two important chemical properties of each of the following: [4]
(i) Monosaccharides
(ii) Proteins .
(b) What are restriction enzymes ? How do thev act ? Give any two examples of restriction enzymes. [4]
(c) What are derived lipids ? Give an example. [2]
Answer:
(a) (i) Chemical properties of monosaccharides :
When a & p isomeric forms of D-glucose are dissolved in water. Their optical rotation changes with time and approaches the final equilibrium value. +53°. This change is known as mutarotation. Mutarotation occurs because of slow conversion of α -D glucose and β-D glucose via open chain form until equilibrium is established giving a constant rotation +53°.

Acetals traditionally derive from the product of the reaction of an aldehyde with excess of alcohol, whereas the name ketal derives from the product of the reaction of a ketone with excess alcohol.

(ii) Chemical properties of proteins :

• Proteins when hydrolyzed by acidic agents, like cone. HC1 yield amino acids in the form of their hydrochlorides.
• Sanger’s reaction : Proteins react with FDNB reagent to produce yellow coloured derivative, DNB amino acid.
• Xanthoproteic test: On boiling proteins with cone. HN03, yellow colour develops due to presence of benzene ring.
• Folin’s test: This is a specific test for tyrosine amino acid, where blue colour develops with phosphomolybdotungstic acid in alkaline solution due to presence of phenol group.

(b) The restriction enzymes are called ‘molecular scissors’. Restriction enzymes are DNA-cutting enzymes present in bacteria. They are obtained from them for use in genetic enginccring-rDNA technology. As sequence are cut within the DNA molecule, they are often called restriction endonucleases.

A restriction enzyme recognizes and cuts DNA only at a particular sequence of nucleotides. For example, the bacterium Hemophilus aegypticus produces an enzyme named Hae III that cuts DNA whenever it identifies the recognition sequence.

A cut is made between the adjacent G and C. HaeIII cleaves both the strands of DNA at the same base pairs producing “blunt” ends.
Examples : EcoRI, HindIII and Bam HI.

(c) Derived lipids are either lipid-like chemicals (e.g., sterols) or derivatives of lipids e.g., terpenes. Prostaglandis and Choline. They are derived from simple and compound lipids by hydrolysis.

Question 3.
(a) Give an account of various enzymes that play a role in the process of DNA replication. [4]
(b) Write short notes on : [4]
(i) Secondary structure of proteins
(ii) Designer oils.
(c) What is meant by synchronization of cell culture. [2]
Answer:
(a) Topoisomerase : Cause single strand breaks and religation.
Helicase: Unwounds a portion of the DNA Double Helix.
RNA Primase : Attaches RNA primers to the replicating strands.
DNA Polymerase delta (δ) : Binds to the 5′ – 3′ strand in order to bring nucleotides and synthesise the daughter leading strand.
DNA Polymerase epsilon (a): Binds to the 3′ – 5′ strand in order to synthesise discontinuous segments starting from different RNA primers.
Exonuclease (DNA Polymerase I): Identifies and removes the RNA Primers.
DNA Ligase : Adds phosphate in the remaining gaps of the phosphate – sugar backbone.
Nucleases : Remove wrong nucleotides from the daughter strand.

(b) (i) Secondary Structure (2° structure): It is development of new stearic relationships amongst the amino acids for protecting their peptide bonds through formation of intrapolypeptide and interpolypeptide hydrogen bonds. Secondary structure is of three types — α-helix, β-pleated and collagen helix. The prefixes α and β signify the first and second types of secondary structure discovered by Pauling and Corey (1951).

α-Helix : The polypeptide chain is spirally coiled, generally in a clockwise or right¬handed fashion (Fig ). There are 3.6 amino acid residues per turn of the spiral. The . spiral is stabilized by straight hydrogen bonds between imide group (-NH-) of one amino acid and carbonyl group (-CO-) of fourth amino acid residue. In this way all the imide and carbonyl groups become hydrogen bonded. R-groups occur towards the outer side of a-helix. a-helix is the final structure in certain fibrous proteins, e.g., keratin (hair, nail, horn), epidermin (skin).

β-Pleated Sheets : Two or more polypeptide chains come together and form a sheet. Condensation is little. However, twisting does occur. The same polypeptide may fold over itself to form two strands for β-pleating. Adjacent polypeptide chains may occur in parallel (e.g., p-keratin) or antiparallel (e.g., silk fibroin). Straight hydrogen bonds occur between imide (-NH-) group of one polypeptide and carbonyl (-CO-) group of adjacent polypeptide. Cross-linkages help in stabilisation of p-pleated sheets.

Collagen Helix : Collagen has a large amount of glycine (25%) and proline (and hydroxyprohne, 25%). It cannot form a-helix due to them. Three of its polypeptide each having about 1000 amino acid residues, come together with each forming an extended left-handed helix. They run parallel, form a right-handed super-helix that is stabilised by hydrogen bonds amongst the three. The triple helix of collagen is often called tropo-collagen. Its one end is stabilised by -S-S- linkages amongst the three chains. Collagen occurs in those tissues where extensibility is limited, e.g., connective tissue, tendons, bones.

(ii) Designer Oil: “Designer oif’ that reduces LDL (“bad”) blood cholesterol levels in humans and increases energy expenditure, which may prevent people from gaining weight. The oil incorporates a phytosterol-based functional food ingredient Phytrol (TM) from Forbes into oil using proprietary technology.

(c) Cell culture synchronisation : Cells in suspension cultures vary greatly in size, shape, DNA, and nuclear content. Moreover, the cell cycle time varies considerably within individual cells. Therefore, cell cultures are mostly asynchronous. It is essential to manipulate the growth conditions of an asynchronous culture in order to achieve a higher degree of synchronisation. A synchronous culture is one in which the majority of cells proceed through each cell cycle phase (Gl, S, G2 and M) simultaneously. Synchronisation can be achieved by following methods.

• Physical methods include selection by volume (size of cell aggregate.)
• Chemical methods include starvation (depriving suspension cultures of an essential growth compound and culture supplying).
• Chemical methods include inhibition (temporarily blocking the progression of events in the cell cycle using a biochemical inhibitor and then releasing the block).

Question 4.
(a) Write the steps in the process of activation of amino acids during the process of translation. [4]
(b) What is the significance of genetic code in protein synthesis ? Mention four important characteristics of the genetic code. [4]
(c) Name the important steps in a single cycle of polymerase chain reaction. [2]
Answer:
(a) The adapter function of the tRNA molecules require the charging of each specific tRNA with its specific amino acid. Since there is no affinity of nucleic acids for specific functional groups of amino acids, this recognition must be carried out by a protein molecule capable of recognizing both a specific tRNA molecule and a specific amino acid.

Activating enzymes called aminoacyl-tRNA synthetases couple each amino acid to its appropriate set of tRNA molecules. There are 20 synthetases for each of the 20 natural amino acids. The reaction involves two steps :

The amino acid-tRNA bond is a high-energy linkage that easily reacts with the amino group of the next amino acid in a protein sequence to form a peptide bond during protein synthesis.

(b) Messenger RNA contains a triplet sequence of nitrogen bases which code for the specific amino acids, used to make polypeptide chains. Each of the sets of three bases is known as a codon or genetic code.

Translation starts with a chain initiation codon (start codon). The most common start codon is AUG which is read as methionine or, in bacteria, as formyl methionine. The three stop codons have been given names : UAG is amber, UGA is opal, sometimes also called umber and UAA is ochre. Stop codons are also called “termination” or “non-sense” codons.

Characteristics of Genetic Code

• Triplet code : Three adjacent nitrogen bases constitute a codon which specifies the placement of one amino acid in a polypeptide.
• Start signal: Polypeptide synthesis is signaled by AUG or methionine codon and GUG — Valine codon. They have dual function.
• Stop signal: Polypeptide chain termination is signaled by three termination codons — UAA, UAG and UGA. They do not specify any amino acid and are hence also called non-sense codon.
• Universal code : The genetic code is applicable universally i.e., the codon specifies the same amino acid from a virus to a tree or human being.
• Non-ambiguous codon : One codon specifies only one amino acid and not any other.

(c) PCR Stages:

• Denaturation step
• Primer Annealing step
• Extension/elongation step (Polymerization)

Question 5.
(a) Write notes on : [4]
(i) Proteomics.
(ii) De-differentiation and Re-differentiation.
(b) Mention the objectives of germplasm conservation using the cell culture technique. What are the limitations of conservation of germplasm using conventional methods? [4]
(c) The base sequence of one strand of DNA is 3′ CATGAC 5′. What will be the base sequence of its : [2]
(i) Complementary DNA strand.
(ii) Complementary RNA strand.
Answer:
(a) (i) Proteomics is the identification, analysis and large scale characterisation of proteome (i.e., the total protein components) expressed by any given cells, tissues and organs under the defined conditions. The major objectives of proteomics are

• to characterise post- transcriptional modifications in protein, and
• to prepare 3D map of cell indicating the exact location of protein.

Proteomics is the direct outcome of advancement made for nucleotide sequencing of different genomes in large scale. This helps to identify various proteins. Generation of information about protein is necessary. Because, protein governs the phenotypic characters of the cells. Merely genome study cannot provide the understanding of mechanism of disease development and various developmental changes occurring in organisms including humans. Moreover, target drugs for many kinds of diseases can be prepared only after understanding the protein modification and protein functions. There are many areas of modem proteomics such as protein expression, protein structure, protein localisation, protein-protein interaction, etc.

(ii) Dedifferentiation: It is a cellular process which occurs in lower life forms such as worms and amphibians in which a partially or terminally differentiated cell reverts to an earlier developmental stage.

Redifferentiation : It is a process by which a group of once differentiated cells return to their original specialised form.

(b) Germplasm Conservation:
The sum total of all the genes present in a crop and its related species constitutes its germplasm; it is ordinarily represented by a collection of various strains and species. Germplasm provides the raw materials (= genes), which the breeder uses to develop commercial crop varieties. Therefore, germplasm is the basic indispensable ingredient of all breeding programmes, and a great emphasis is placed on collection, evaluation and conservation of germplasm.

Limitations of conventional methods:

• Conventionally, germplasm is conserved as seeds stored at ambient temperature, low temperature or ultralow temperature. But many crops produce recalcitrant or short-lived seeds, and in case of clonal crops seeds are not the best material to conserve in view of their genetic heterogeneity and unknown worth.
• Roots and tubers loose viability rapidly and their storage requires large space, low temperature and is expensiv e.
• In addition, materials modified by genetic engineering may sometimes be unstable, and hence may need to be conserved intact for future use.

In such cases, the following approaches of germplasm conservation may be applied:

• freeze preservation,
• slow-growth cultures.
• DNA-clones and
• desiccated somatic embryos/artificial seeds.

(c) DNA -3′ CATGAC 5′

• COMPLIMENTARY DNA: 5′ GTACTG 3′
• COMPLIMENTARY RNA: 5′ GUACUG 3′

Question 6.
(a) Why are enzymes called biocatalysts ? Briefly discuss the mode of enzyme action. [4]
(b) Explain the principle and applications of each of the following biochemical techniques: [4]
(i) Gel permeation.
(ii) Colorimetry.
(c) How are the diseases cystic fibrosis and albinism caused? [2]
Answer:
(a) Catalysts are chemical substances used to speed up chemical reaction without any change of its own. In biological systems, certain biomolecules known as enzymes act in the same manner i.e., they mediate different biochemical reactions but themselves remain unaltered so they are termed as biocatalysts.
Mode of enzyme action : It could be explained by following models :

(b) (ii) Colorimetry
Principle : Colorimetry is the technique of determining the concentration of a chemical in a solution, if it has a colour, is to measure the intensity of the colour and relate the intensity of the colour to the concentration of the solution. In colorimetry, two fundamental laws are applied :

• firstly , a Lambert’s law. relates the amount of light absorbed and the distance it travels through an absorbing medium; and
• Secondly, Beer’s law relates light absorption and the concentration of the absorbing substance.

Application : It is used extensively for identification and determination of concentrations of substances that absorb light (any colour solution). A simple application lies in comparing intensities of radiation transmitted through layers of different thicknesses of two solutions of the same absorbing substance, one with a known concentration, the other unknown.

(c) Cystic fibrosis: A disease that results from a decrease in fluid and salt secretion by a transport protein known as Cystic Fibrosis Transmembrane Regulator (CFTR). As a result of this defect secretion from the pancreas is blocked and heavy dehydrated mucus accumulates in the lungs leading to chronic lung infection.

Albinism: It is a recessive disorder due to non-conversion of typosine into melanin because of gene mutation.

Albinism are of two types :

• Type 1 albinism is caused by defects that affect production of the pigment, melanin.
• Type 2 albinism is due to a defect in the ‘P” gene. People with this type have slight coloring at birth.

Question 7.
(a) Explain how ‘Dolly’ was created. What is its importance in the field of biotechnology? [4]
(b) Differentiate between: [4]
(i) PCR and Gene Cloning.
(ii) Batch Culture and Continuous Culture.
(c) What are polysaccharides ? How are they formed? [2]
Answer:
(a) Dolly, was the first mammal to be cloned by Wilmut et. al (1977). Dolly was the end result of a long research program founded by the British government at the Roslin Institute in Scotland. They used the technique of somatic cell nuclear transfer, where the cell nucleus from an adult udder cell is transferred into an unfertilized oocyte that has had its nucleus removed. The hybrid cell is then stimulated to divide by an electric shock, and the blastocyst that is eventually produced is implanted in a surrogate mother. Dolly was the first clone produced from a cell taken from an adult animal.

The following steps are involved in creation of Dolly :
Isolate donor nucleus : Isolate the nucleus from a somatic (non-reproductive) cell of a udder of adult donor sheep. The nucleus contains all the complete genetic material of the organism. A very small needle and syringe (suction device) is used to penetrate through the cell membrane to hold the nucleus and remove it from the cell.

Get unfertilized eggs: Retrieve some unfertilized egg cells (reproductive) from a female sheep. Many eggs are needed since not all of them will survive the various steps of cloning.

Remove the egg’s nucleus: Remove the egg cell’s nucleus, which contains only one-half of the sheep’s genetic material.

Insert donor nucleus : Insert the nucleus, with all its complete genetic material, isolated from the donor sheep mammal in Step 1 into the cytoplasm of egg cell that has no nuclear material. The egg’s genetic material now contains all traits from the donor adult. This egg is genetically identical to the donor adult cells.

Transfer the egg into womb : Transfer the egg into a receptive female sheep’s womb. Those eggs that survive and implant will continue to develop into embryos. When the offspring is born, it is a clone (genetically identical) of the donor sheep. After cloning was successfully demonstrated through the production of Dolly, many other large mammals have been cloned, including horses and bulls.

(b) (i) PCR:

• Amplification of desired segment of DNA within hours.
• No host cell required.

Gene cloning:

• Amplification of a desirable gene takes more time under lab condition.
• Host cell is required.

(ii) Batch culture:

• In this culture, the same medium and all the cells produced are retained in the culture vessel. Fresh medium is not added.
• The cell number of biomass exhibits a typical sigmoid curve.

Continuous culture:

• In this culture, both cells and used medium are taken out from the continuous culture and replaced by equal volume of fresh medium.
• Here, the cell population is a maintained in a steady state by regularly replacing a portion of used or spent medium.

(c) Polysaccharides are complex polymeric carbohydrate structures, formed by polymerization of monomeric repeating units (either mono-or di-saccharides) joined together by glycosidic bonds.
Example: starch, glycogen, etc. Polysaccharides are formed by enzyme catalyzed condensation reaction between any number of saccharide units.

Starch : It is the nutritional reservoir of plants. They are formed by the polymerisation/condensation of glucose molecules. Two types of starch are possible unbranched starch known as Amylase and branched starch known as Amylopectin. They actually differ in glycosidic linkage.

Glycogen : It is the storage form of glucose in animals. Two chains of glucose molecules joined by an alpha-1, 4-glycosidic bonds are linked by an alpha-1. 6-glycosidic bond to create a branch point.

Question 8.
(a) Briefly explain the concept and application of: [4]
(i) In vitro pollination.
(ii) Protoplast fusion.
(b) Mention the significance of plants obtained by each of the follow ing types of plant tissue culture techniques : [4]
(i) Endosperm culture.
(ii) Anther culture.
(c) State the main achievements of the Human Genome Project. [2]
Answer:
(a) (i) Pollination and fertilization under in vitro conditions offer an opportunity for producing hybrid embry os among plants that cannot be crossed by conventional methods of plant breeding. In nature, Intergeneric or Interspecific hybridization occurs very rarely. This is due-to barriers hindering the growth of the pollen tube on the stigma or style. In such cases, the style or part of it can be excised and pollen grains either placed on the cut surface of ovary or transferred through a hole in the wall of ovary. This technique, called intraovarian pollination, has been successfully applied in such species as Papaver somniferum, Eschscholtiza California, Argemone mexicana.

Ovular Pollination : In this in vitro pollination method, pollen tubes directly penetrate isolated ovules. Interspecific crossing barriers do not occur during penetration of the pollen tubes into the micropyle. Completion of pollen tube penetration is much earlier than the division of the generative cell in sperm cells which may be the primary cause for the failure in fertilization.

Placental Pollination : In this in vitro pollination method, the ovaries are cut into sectors on the day or after the day of stigma receptivity. Each sector contains a placenta with a row of ovules without or with ovary wall. Pollens are abundantly applied on the placenta. In this case also the rate of fertilisation is very slow.

Applications of in vitro Pollination : In plant breeding, the technique of in vitro pollination has lot of potential in at least three different areas,

• overcoming self-incompatibility,
• overcoming cross-incompatibility,
• haploid production through parthenogenesis.

(ii) The technique for protoplast fusion are pritty will defined and highly effective for almost all the systems. Protoplast of desired species/strains are mixed in almost equal proportion; generally they are mixed while still suspended in the enzyme mixture. The protoplast mixture is then subjected to high pH (10.5) and high Ca²⁺ concentration 50 m molL^-1 at 37°C for about 30 min. (high pH Ca²⁺ treatment). This technique is quite suitable for some species while for some other it may be toxic.

Two types of protoplast fusions are :
Spontaneous protoplast fusion: During isolation of protoplasts for culture, when enzymatic degradation of cell walls is affected, some of the protoplasts, lying in close proximity, may undergo fusion to produce homokarvons or homokaryocytes. each with 2-40 nuclei. The occurrence of multinucleate fusion bodies is more frequent, when protoplasts are prepared from actively dividing cells.

This spontaneous fusion, however, is strictly intraspecific. How ever, spontaneous fusion of protoplasts can also be induced by bringing protoplasts into intimate contact through micromanipulators or micropipettes.

There seems to be a correlation between the size of the leaf and the percentage of protoplasts undergoing spontaneous fusion; protoplasts from young leaves are more likely to undergo this fusion.

Induced protoplast fusion: Somatic hybridization is generally used for fusion of protoplasts either from two different species (inter specific fusion) or from two diverse sources belonging to the same species. To achieve this objective, spontaneous fusion may be of no value, and induced fusion requiring a suitable agent (fusogen) is necessary. In animals, inactivated Sendai virus is needed to induce fusion.

In plants, however, the inducing agent first brings the protoplasts together and then causes them to adhere to one another for bringing about fusion. During the last two decades, a variety of treatments have been successfully utilized for fusion of plant protoplasts. These treatments particularly include the following : NaN0₂, high pH with high Ca⁺⁺ ion concentration and polyethylene glycol (PEG).

Applications: Auxin independent growth of hybrids of Nicotiana glauca and A. langsdorffii. Two parental lines cannot produce auxin and thus do not grow on auxin free medium, the hybrid cells produce auxin and are they able to grow and form callus.

(b) (i) Endosperm culture: The endosperm nurses the developing zygotic embryo. For the first time Lamp and Mills (1933) grew7 maize endosperm on nutrient medium 10-20 days after pollination. The endosperm proliferated slightly. In 1949, LaRue succeeded to produce callus from immature endosperm. From India, B.M. Johri and S.S. Bhojwani (1965) at the University of Delhi reported and endosperm culture. Some examples of triploid plants raised from endosperm cultures are : Asparagus officinalis, barley (Hordeum vulgare), rice (Oryza sativa), maize (Zea mays), Prunus persica, Pyrus malus, Citrus gradis, sandle plant (Santalum album).

The triploid plants are self-sterile and usually seedles. This characteristic increases edibility of fruits and desirable in plants such as apple, banana, grape, mulberry, mango, watermelon, etc. These are commercially important edible fruits. The triploids of poplar {Populus tremuloides) have better quality pulpwood. Therefore, it is important to the forest industry,

(ii) Anther culture: When anthers of some plants are cultured on suitable medium to produce haploid plants, it is called anther culture. For the first time S. Guha and P. Maheshwari (1964) produced haploid embryos in vitro from isolated anthers of Datura innoxia. Haploid production has immense use in plant breeding and improvement of crop plants. Haploids provide an easier system for induction of mutation. They can be employed for rapid selection of mutants having traits for disease resistance. The Institute of Crop Breeding and Cultivation (China) has developed the high yielding and blast resistant varieties of rice zhonghua No. 8 and zhonghua No.9 through transfer of desired alien gene.

It is highly useful for the improvement of many crop plants. It is also useful for immediate expression of mutations and quick formation of purelines. This technique was first used in India to produce haploids of Datura. In many plants haploids are also produced by culturing unfertilized ovaries/ovules. In pollen grain culture pollen grains are eseptically removed from the anther and cultured on liquid medium.

(c) The Human Genome Project was an international scientific research project that determined the DNA sequence of the approximately 30,000 — 35,000 genes that make-up the human genome. The greatest achievement of this project is that scientists can find out the structure of human genes and successfully trace the structure of genes. It has been possible to develop the technique regarding the treatment of defective genes only because of the human genome project.

The treatment of the hereditary diseases like cancer has been easier because of this project. DNA interference is a recently developed technique regarding treatment by which it would be possible to treat many incurable diseases. Along with this, the development of human, physical and mental structure etc., are the main achievements of human genome project.

Question 9.
(a) What type of information is obtained from each of the following database. [4]
(i) Taxonomy Browser
(ii) PDB.
(iii) GENSCAN
(iv) PIR.
(b) Explain the method of DNA sequencing using automated DNA sequencing technique. [4]
(c) Write any two examples of each of the following plant hormones commonly used in media preparation: [2]
(i) Auxins.
(ii) Cytokinins.
Answer:
(a) (i) Taxonomy browser: This search tool provides taxonomic information on various species. The Taxonomy database of NCBI has information (including scientific and common names) about all organisms for which some sequence information is available (over 79,000 species).

The server provides genetic information and the taxonomic relationship of the species in question. Taxonomy has links with other servers of NCBI e.g., structure and PubMed.

(ii) PDB (Protein Data Bank) : This database has sequence of those protein whose 3-D structures are known.
Source: NCBI-U.S.A.; EBI, UK.

(iii) Genscan is a notable example of Eukaryotic ab initio gene finders. Genscan is one of the best gene finding algorithms for sequence alignment and gene prediction.

(iv) PIR is a non-redundant annotated protein sequence database, and analytical tools.

(b) Automatic DNA Sequencers: Automatic sequencing machines were developed during 1990’s. It is an improvement of Sanger’s method. In this new method, a different fluorescent dye is tagged to the ddNTP’s. Using this technique, a DNA sequence containing thousands of nucleotides can be determined in a few hours. Each dideoxynucleotide is linked with a fluorescent dye that imparts different colors to all the fragments terminating in that nucleotide. All four labelled ddNTP’s are added to a single capillary tube. It is a refinement of get electrophoresis which separates fastly. DNA fragments of different colors are separated by their size in a single electrophoretic gel.

A current is applied to the gel. The negatively charged DNA strands migrate through the pores of gel towards the positive end. The small sized DNA fragments migrate faster and vice-versa. All fragments of a given length migrate in a single peak. The DNA fragments are illuminated with a laser beam. Then the fluorescent dyes are excited and emit light of specific wavelengths which is recorded by a special ‘recorder’. The DNA sequences are read by determining the sequence of the colours emitted from specific peaks as they pass the detector. This information is fed directly to a computer which determines the sequence. A tracing electrogram of emitted light of the four dyes is generated by the computer. Colour of each dye represents the different nucleotides. Computer converts the data of emitted light in the nucleotide sequences.

(c) (i) IAA (Indole 3-Acetic Acid) and 2, 4-Dichlorophenoxyacetic acid (2, 4-D)
(ii) Kinetin and BAP (Benzyl Amino purine)

ISC Class 12 Biotechnology Previous Year Question Papers

ISC Biotechnology  Previous Year Question Paper 2012 Solved for Class 12

Maximum Marks: 80
Time allowed: Three hours

• Candidates are allowed additional 15 minutes for only reading the paper. They must NOT start writing during this time.
• Answer Question 1 (Compulsory) from Part I and five questions from Part II, choosing two questions from Section A, two questions from Section B and one question from either Section A or Section B.
• The intended marks for questions or parts of questions are given in brackets [ ].
• Transactions should be recorded in the answer book.
• All calculations should be shown clearly.
• All working, including rough work, should be done on the same page as, and adjacent to the rest of the answer.

Part-1
(Answer all questions)

Question 1.
(a) Mention any one significant difference between each of the following: [5]
(i) Hybrid and Cybrid.
(ii) DNA polymerase and Taq DNA polymerase.
(iii) Glycosidic bond and Peptide bond,
(iv) Oils and Waxes.
(v) Homopolysaccharide and Heteropolysaccharide.

(b) Answer the following questions : [5]
(i) What is a callus?
(ii) Name the method used for the sterilization of plant hormones and vitamins.
(iii) Why is DNA replication called semi-conservative replication?
(iv) What is a promoter gene?
(v) State two uses of stem cells.

(c) Write the full form of the following :
(i) HGP
(ii) STS
(iii) CSIR
(iv) LAF
(v) SCP

(d) Explain briefly:
(i) Amphipathic property of lipids.
(ii) Replication fork
(iii) Androgenesis
(iv) Transamination.
(v) Active site.
Answer:
(a) (i) Hybrid: Plants produced through the fusion of protoplasts of two different plant species/varieties is called hybrid.

Cybrid: Cybrid or cytoplasmic hybrid are cells or plant containing nucleus of one species but cytoplasm from both the parental species.

(ii) DNA polymerase: A DNA polymerase is an enzyme that catalyzes the polymerization of deoxyribonucleotides into a DNA strand in DNA replication.

Taq DNA polymerase: Taq polymerase, is a thermostable DNA polymerase, originally isolated from bacterium Thermits aquaticus. It is used in polymerase chain reaction.

(iii) Glycosidic bond: A glycosidic bond (C-O-C) is a type of covalent bond that joins a aldose or ketone group of a carbohydrate (sugar) molecule to another group (OH) which may or may not be another carbohydrate.

Peptide bond: A peptide bond (HN – C = 0) is a chemical bond formed between two amino acids when the carboxyl group of one amino acid molecule reacts with the amino group of the other amino acid molecule. thereby releasing a molecule of water.

(iv) Oils: Oils are the esters of unsaturated fatty acid with glycerol. Oils are liquid at room temperature and have low melting point.

Waxes: Waxes are esters of fatty acid other than glycerol. They contain one molecule of long chain fatty acid esterified with one molecule of long chain like cytyl, ceryl or mericvl, mono hydroxy’ alcohol.

(v) Homopolysaccharide: Homopolysaccharides are the complex carbohydrates formed by polymerisation of the monosaccharide monomers.

Heteropolysaccharide: Heteropoly saccharides are the complex carbohy drates w hich are produced by the condensation of more than one type of monosaccharide monomers or their derivatives e.g., chitin, agar.

(b) (i) Callus is a mass of meristematic, undifferentiated cells derived from plant tissue (explants).

(ii) The autoclaving denatures the vitamins and hormones, therefore, the solution of these compounds are sterilized by using Millipore filter paper with pore size of 0.2 micrometer diameter.

(iii) Semi-conservative is that mode of replication in which out of the two DNA strands, one is conserved strand and the other is newly synthesised.

(iv) A promoter gene is a segment of DNA containing the enzyme RNA polymerase that initiates the transcription of the genetic code.

(v) Uses of stem cells :
(1) Bone marrow transplants that are used to treat leukemia (blood cancer).
(2) Treatment for muscular dystrophy.

(c) (i) HGP: Human Genome Project.

(ii) STS: Sequence Tagged Sites.

(iii) CSIR : Council of Scientific and Industrial Research.

(iv) LAF: Laminar Air Flow.

(v) SCP: Single Cell Protein. .

(d) (i) Amphipathic nature : Most membrane lipids are amphipathic, having a non-polar end and a polar end. The amphiphilic nature of some lipids allows them to form structures such as vesicles, liposomes, or membranes in an aqueous environment.

(ii) The point at which the two strands of DNA are separated to allow replication of each strand is known as replication fork.

(iii) Androgenesis is the development of an embryo containing only paternal chromosomes due to failure of the egg to participate in fertilization.

(iv) Transamination is the process of transfer of the a-amino group from the amino acid to an a-keto acid.

(v) Active site is part of an enzyme where substrates bind and undergo a chemical reaction.

Part-II
(Answer any five questions)

Question 2.
(a) Explain the general structure of an amino acid. What do you understand by essential and non-essential amino acids? [4]
(b) What are cloning vectors ? Write the main characteristics of any three types of cloning vectors. [4]
(c) What is a Codon ? Name the start codon and any one end codon. [2]
Answer:
(a) Amino acids are building blocks of macromolecular proteins. They contain amino group and carboxyl group as functional groups.
On the basis of nutritional values amino acids are of two types :
Essential amino acids : These are essential for our body but they are not synthesised inside our body are termed as essential amino acids e.g., valine, leucine, isoleucine, lysine, phenylalanine, methionine, threonine, histidine, arginine.

Non-essential amino acids : They are those which are synthesised through transformation and transamination inside our body e.g., serine, alanine etc.

(b) Cloning vector is a self-replicating DNA molecule that carries foreign DNA insert into a host cell, replicates inside a bacterial (or yeast) cell and amplify to produce many copies of itself and the foreign DNA.

Plasmid: It is an extra chromosomal circular DNA molecule that self replicates inside the bacterial cell and some yeast; cloning limit: 100 to 10,000 base pairs or 0.1-10 kilobases (kb).

Phage : Designed bacteriophage lambda (A.) and Ml 3 : linear DNA molecules, whose region can be replaced with foreign DNA without disrupting its life cycle; cloning limit: 8-20 kb. M13 is a filamentous phage which infects E-coli. Cloning limit: 10 kb.

Cosmids: A constructed extrachromosomal circular DNA molecule that combines features of plasmids and ‘cos’ site of phage ; cloning limit – 45 kb.

Yeast Artificial Chromosomes (YAC) : An artificial chromosome that contains telomeres, origin of replication, a yeast centromere, restriction enzyme site and a selectable marker for identification in yeast cells ; cloning limit: 1 Mb.

(c) Codon is a unit of genetic coding, consists of a series of three adjacent bases (triplet) in one polynucleotide chain of a DNA or RNA molecules, which codes for a particular amino acid during synthesis of proteins in a cell. For example, ATA codes for Leucine.

Start codon : The codon AUG specifies the first amino acid, methionine, in protein synthesis.

End codon : UAG also referred to as amber codon, in mRNA which terminate translation.

Question 3.
(a) Briefly explain the structure of a tRNA molecule. Mention its function during the process of protein synthesis. [4]
(b) Give the stepwise procedure of sequencing of DNA by Sanger’s method. [4]
(c) What is Totipotency ? Give an example of a Totipotent cell. [2]
Answer:
(a) Transfer RNA (tRNA) : It is also called soluble or sRNA. There are over 100 types of tRNAs. Transfer RNA constitutes about 15% of the total RNA. tRNA is the smallest RNA with 70-85 nucleotides and sedimentation coefficient of 4S. The nitrogen bases of several of its nucleotides get modified e.g., pseudouridine (φ), dihydrouridine (DHU), inosine (I). This causes coiling of the otherwise single-stranded tRNA into L-shaped form (three-dimensional, Klug, 1974) or clover-like form (two dimensional, Holley, 1965). About half of the nucleotides are based paired to produce paired stems. Five regions are unpaired of single-stranded—AA-binding site, Tig C loop, DHU loop, extra arm and anticodon loop.

• Anticodon. It is made-up of three nitrogen bases for recognizing and attaching to the codon of wRNA.
• AA-Binding site. It lies at the 3′ end opposite to the anticodon and has CCA — OH group (5′ ends bears G). Amino acid or AA-binding site and anticodon are the two recognition sites of tRNA.
• T φ C loop. It contains pseudouridine. The loop is the site for attaching to ribosomes,
• DHU loop. The loop contains dihydrouridine. It is binding site for aminoacyl synthetase enzyme,
• Extra arm. It is a variable site arm or loop which lies between T ig C loop and anticodon. The exact role of extra arm is not known.

Functions:
tRNA is adapter molecule which is meant for transferring amino acids to ribosomes for synthesis of polypeptides. There are different tRNAs for different amino acids. Some amino acids can be picked up by 2-6 tRNAs. tRNAs carry specific amino acids at particular points during polypeptide synthesis as per codons of mRNA. Codons are recognised by anticodons of tRNAs. Specific amino acids are recognised by particular activating or aminoacyl synthetase enzymes,

They hold peptidyl chains over the mRNAs. The initiator tRNA has the dual function of initiation of protein synthesis as well as bringing in of the first amino acids. There is, however, no tRNA for stop signals.

(b) DNA sequencing: It is the determination of the precise sequence of nucleotides in a sample of DNA.

Sanger dideoxy method: The most popular method for DNA sequencing is called the dideoxy method or Sanger method (named after its inventor, Frederick Sanger, who was awarded the 1980 Nobel prize in chemistry).

The Procedure : The DNA to be sequenced is prepared as a single strand.
This template DNA is supplied with

a mixture of all four normal (deoxy) nucleotides in ample quantities

• dATP
• dGTP
• dCTP
• dTTP

a mixture of all four dideoxynucleotides, each present in limiting quantities and each labeled with a tag.

• that fluoresces a different color :
• dd ATP
• dd GTP
• dd CTP
• dd. TTP

DNA polymerase 1

Because all four normal nucleotides are present, chain elongation proceeds normally until, by chance, DNA polymerase inserts a dideoxy nucleotide (shown as colored letters) instead of the normal deoxvnucleotide (shown as vertical lines). If the ratio of normal nucleotide to the dideoxy versions is high enough, some DNA strands will succeed in adding several hundred nucleotides before insertion of the dideoxy version halts the process.

At the end of the incubation period, the fragments are separated by length from longest to shortest. The resolution is so good that a difference of one nucleotide is enough to separate that strand from the next shorter and next longer strand. Each of the four dideoxynucleotides fluoresces a different color when illuminated by a laser beam and an automatic scanner provides a printout of the sequence.

Limitation : Limitations include non-specific binding of the primer to the DNA, affecting accurate read-out of the DNA sequence, and DNA secondary structures affecting the fidelity of the sequence

(c) Cellular totipotency : Totipotency is the ability of a single cell to divide and produce all the differentiated cells in an organism, including extraembryonic tissues and also the formation of a new organism. Totipotent cells formed during sexual and asexual reproduction include spores and zygotes.

Question 4.
(a) Briefly describe the essential components of the nutrient medium used for the plant tissue culture technique. Also, write the names of any two plant tissue culture media frequently used in the laboratory . [4]
(b) With reference to suspension culture, explain the following : [4]
(i) Achemostat.
(ii) A turbidostat.
(c) What are purines and pyrimidines ? Where are they located in a cell? [2]
Answer:
(a) Nutrient Medium : Virtually all tissue culture media are synthetic or chemically defined; only a few of.them use complex organics, e.g., potato extract, as their normal constituents. A synthetic medium consists of only chemically defined compounds. A variety of recipes have been developed since none of them is suitable for either all plant species or for every purpose. Most of these recipes have been elaborated from those of White (itself evolved from a medium for algae) and Gautheret (based on Knop’s salt solution) The composition is as follow :

Inorganic nutrients: In addition to C, H and O, all nutrient media provide the 12 elements essential for plant growth, viz., N, P, K, Ca, S, Mg (these six are called macronutrients, and are needed in concentrations >0.5 mmol L^-1 or > 0.5 mM), Fe, Zn, Mn Cu, B and Mo (these six are known a micronutrients, and are required in concentrations <0.5 mmol L” ’ ) Generally, iron is provided as iron.EDTAcomplex to keep it available at higher (>5.8) pH. Nitrate is superior to ammonium as the sole N source, but use of NH+ checks the drift of pH towards alkalinity.

Vitamins : For optimum callus growth, the following vitamins are required . inositol, thiamine, pyridoxine and nicotinic acid of which thiamine is essential and the rest are promotory. Pantothenic acid is also known to be promotory but is not included in most of the recipes.

Carbon source : Sucrose (20-50 g L) is the most commonly used carbon source for all cultured plant materials, including even green shoots. In some systems, e.g., monocots, glucose may be superior to sucrose. Plant tissue can utilize other sugars like maltose, galactose, lactose, mannose and even starch but these are rarely used.

Growth regulator: The following growth regulators (GRs) are used in plant tissue culture. Auxins, e.g., IAA (indole-3-acetic acid), IBA (indole-3-butyric acid), NAA (napthalene acetic acid), NOA (naphthoxy acetic acid), 2, 4-D (2,4-dichlorophenoxy acetic acid) etc., are commonly used to support cell division and callus growth (especially 2. 4-D), somatic embryo (SE) induction, rooting, etc. Cytokinins like kinetin (furfurylamino purine), BAP (benzylamino purine), zeatin, 2-ip (isopentenyl adenine), TDZ (thidiazuron, a compound having cytokinin activity) are employed to promote cell division, regeneration of shoots often SE induction and to enhance proliferation and growth of axillary buds. Abscisic acid (ABA) promotes SE and shoot bud regeneration in many species are markedly improves SE maturation. Of the over 20 gibberellins known, GA₃ is almost exclusively used. It promotes shoot elongation and SE germination.

Complex organic additives: In earlier studies, complex additives like yeast extract, coconut milk, casein hydrolysate, com milk, malt extract and tomato juice are used to support plant tissue growth. White’s medium, Murashige and Skoog (MS) are the two common media used for plant tissue culture.

(b) (i) Chemostat :A type of cell culture; a component of medium is in a growth limiting concentration; fresh medium is added at regular interv als and equal volume of culture is withdrawn. But in a chemostat, a chosen nutrient is kept in a concentration so that it is depleted very rapidly to become growth limiting, while other nutrients are still in concentrations higher than required. In such a situation, any addition of the growth-limiting nutrient is reflected in cell growth. Chemostats are ideal for the determination of effects of individual nutrients on cell growth and metabolism.

(ii) Turbidostat: A type of suspension culture; when culture reaches a predetermined cell density, a volume of culture is replaced by fresh medium; works well at growth rates close to the maximum. A continuous culturing method where the turbidity of the culture is kept constant by manipulating the rate at which medium is fed. If the turbidity falls, the feed rate is lowered so that growth can restore the turbidity to its start point. If the turbidity rise the feed rate is increased to dilute the turbidity back to its start point.

(c) Purines and pyrimidines are two of the basic units of the nucleic acids. They are found in a DNA and RNA in a cell Purines is a large sized double ring structure. It contains two bases, i.e., adenine and guanine, Pyrimidines are small sized, single ring structures. It contains three type of bases i.e., thymine, cytosine and uracil.

Question 5.
(a) Explain giving an example how recombinant DNA technology can be used for the formation of
the following: [4]
(i) A vaccine.
(ii) A plant with delayed fruit ripening.
(b) What is osmotic pressure ? Explain any one biochemical technique based on osmotic pressure. [4]
(c) What are dextro-rotatory and laevo-rotatory substances? [2]
Answer:
(a) (i) Recombinant vaccines : Vaccine is produced using recombinant DNA technology. A recombinant vaccine contains protein or a gene encoding a protein of a pathogen origin that is immunogenic A gene coding an immunogenic protein from the pathogen, is isolated, cloned and used for vaccine production The vaccines based on recombinant proteins are also called Sub-Unit Vaccines.

Whole protein vaccine : Hepatitis B vaccine is produced from surface antigens of transgenic yeast by r-DNA technology They can also be produced in genetically engineered microbes, cultured animal cells, possibly in insects and plants.

Recombinant – polypeptide vaccines : In some cases, the immunogenic portion of the protein- recombinant polypeptide is used as vaccine e.g., gene encoding B polypeptide (part of cholera enterotoxin – Ab A2 and B polypeptide) has been cloned and the recombinant B polypeptide produced is being used, in combination with inactivated cholera cells, as an oral vaccine in place of conventional injectable cholera vaccine. Immunogenicity of foot and mouth disease virus coat protein is due to its amino acids 114-160 and also 201 -213. They induce antibodies which neutralize the virus and thereby provide protection against the foot and mouth disease.

Live recombinant vaccine : The most advanced and promising approach in which concerned pathogen gene is introduced into the genome of selected viral / bacterial vector which is suitably attenuated and the live microorganisms are used for vaccination. Vaccinia virus appears to be more promising vector.

DNA vaccines: Recently vaccines based on pathogen naked DNA are being developed. Tue various approaches for DNA vaccines are as follow

• injection of pure DNA (or RNA) preparation into muscles
• reimplantation of autologus cells (cells of the individual to be vaccinated) into which the gene has been transferred and
• particle gun delivery of plasmid DNA which contains the gene in an expression casette e.g., skin cells They elicit humoral immune response and are usually shed off in a few days preventing long term persistence modified cells.

(ii) Delayed fruit ripening
A major problem in fruit marketing is the pre-mature ripening and softening dining transport of fruits. Consequently shelf-life of fruit remains short in the market. During ripening, genes encode the enzyme cellulase and polygalacturonase. Therefore, ripening process can be delayed by interfering the expression of these genes. In the U.S.A., a transgenic tomato named FlavrSavr (flavour saver) was produced where ripening is delayed by , lowering polygalacturonase activity.

A plant growth hormone ethylene is produced during fruit ripening and senescence. It is synthesised from S-adenosylmethionine through an intermediate compound 1-aminocyclopropane-l-carboxylic acid (ACC). There is a large number of bacteria that can degrade ACC. Therefore, bacterial gene (for ACC) deaminase associated with ACC degradation was isolated and introduced into tomato. In transgenic tomato, fruit ripening was delayed because it synthesised lower amount of ethylene (due to inhibition in ACC synthesis) than the normal tomatoes. Such tomatoes and other fruits can be transported to a longer distance without spoilage.

(b) The osmotic pressure is defined to be the pressure required to maintain an equilibrium, with no net movement of solvent. Osmotic pressure is a colligative property, meaning that the osmotic pressure depends on the molar concentration of the solute but not on its identity.

In biochemistry, dialysis is the process of separating molecules in solution by the difference in their rates of diffusion through a semi-permeable membrane, such as dialysis tubing. Typically a solution of several types of molecules is placed into a semi-permeable dialysis bag, such as a cellulose membrane with pores, and the bag is sealed. The sealed dialysis bag is placed in a container of a different solution, or pure water. Molecules small enough to pass through the tubing (often water, salt and other small molecules) tend to move into or out of the dialysis bag, in the direction of decreasing concentration. Larger molecules (often proteins, DNA, or polysaccharides) that have dimensions significantly greater than the pore diameter are retained inside the dialysis bag.

(c) Substances which rotate or deviate the plane of polarized light to the right (clockwise) are called dextrorotatory and are indicated by prefixing (+) or d to their names, e.g., d-glucose or (+) glyceraldehydes; Laevorotatory are the substances which rotate or deviate the plane polarized light to the left and are indicated by prefixing L or (–) to their names; e.g., L-alanine or (–) glyceraldehydes.

Question 6.
(a) Write short notes on : [4]
(i) Single nucleotide polymorphism.
(ii) Bioinformatics databases.
(b) How are biomolecules separated by the following techniques: [4]
(i) Chromatography.
() Centrifugation.
(c) Give two differences between enzymes and inorganic catalysts: [2]
Answer:
(a) (i) Single nucleotide polymorphisms, commonly called SNPs (pronounced “snips”), are the most common type of genetic variation in a nucleotide sequence due to change even in a single base among different individuals. Thus, each SNP represents a difference in a single DNA building block, called a nucleotide. For example, a SNP may replace the nucleotide cytosine (C) with the nucleotide thymine (T) in a certain stretch of DNA. In human genome, SNPs occur at 1.6-3.2 million site. Due to the changes in bases SNPs affect the gene function. DNA fingerprinting of individuals is possible due to these genetic variations in non-coding parts of genome.

(ii) Database : A database is an organized collection of data for one or more multiple uses. One way of classify ing databases involves the type of content, for example : bibliographic, full-text, numeric and image.

Biological databases are libraries of life sciences information, collected from scientific experiments, published literature, high-throughput experiment technolog}, and computational analysis. They contain information from research areas including genomics, proteomics, metabolomics, microarray gene expression, and phylogenetics. Information contained in biological databases includes gene function, structure, localization (both cellular and chromosomal), clinical effects of mutations as well as similarities of biological sequences and structures.
Examples:

• ENA (European Nucleotide Archive) – primary nucleotide data, incorporating EMBL- Bank.
• UniProt-protein databases.
• PDB (Protein Data Bank)-biological macromolecular structure.

(b) (i) Chromatography is a technique of separation of biomolecules involves a sampling mixture containing biomolecules being dissolved in a mobile phase (which may be a gas, a liquid or a supercritical fluid) due to their differential adsorption over an adsorbent medium. The mobile phase is then forced through an immobile, immiscible stationary phase. The phases are chosen such that components of the sample mixture have differing solubilities in each phase.

A component which is quite soluble in the stationary phase will take longer to travel through it than a component which is not very’ soluble in the stationary phase but very soluble in the mobile phase. As a result of these differences in mobilities, sample mixture components will become separated from each other as they travel through the stationary’ phase.

Techniques such as H.P.L.C (High Performance Liquid Chromatography) and GC. (Gas Chromatography) use columns—narrow tubes packed with stationary phase, through which the mobile phase is forced. The sample is transported through the column by continuous addition of mobile phase. This process is called elution. The average rate at which an analyte moves through the column is determined by the time it spends in the mobile phase.

(ii) Centrifugation is a process that involves the use of the centrifugal force for the sedimentation of the components of a mixture with a centrifuge. More-dense components of the mixture migrate away from the axis of the centrifuge, while less-dense components of the mixture migrate towards the axis. Chemists and biologists may increase the effective gravitational force on a test tube so as to move rapidly and completely cause the precipitate (‘’pellet”) to gather on the bottom of the tube. The remaining solution is properly called the “supernate” or ‘ supernatant liquid”. The supernatant liquid is then either quickly decanted from the tube without disturbing the precipitate, or withdrawn with a Pasteur pipette. For example, microcentrifuges are used to process small volumes of biological molecules, cells, or nuclei.

(c) Differences between enzyme and inorganic catalyst are mentioned as follows :

Question 7.
(a) Differentiate between : [4]
(i) Prokaryotic genome and Eukaryotic genome.
(ii) Somatic embryo and Zygotic embryo.
(b) Explain how a genomic DNA library is formed. How does it differ from cDNA library ? [4]
(c) Name any two inborn metabolic disorders in human beings. Also, write one main symptom for each of them.
Answer:
(a) (i) Prokaryotic Genome:

• Genome are much smaller and simpler.
• Highly repetitive DNA is not found.
• It is without a limiting membrane.
• It is a naked double strand of DNA.

Eukarvotic Geflorne:

• Genome are larger and complex.
•  Occurrence of highly repetitive DNA is found.
• It is bounded by nuclear membrane.
• Double strand of DNA is associated with histone proteins.

(ii) Somatic Embryo: Somatic embryos are formed from plant cells other than egg that are not normally involved in the development of embry os, e.g., callus or explant. No endosperm or seed coat is formed around a somatic embryo.

Zygotic Embryo: Zygotic embryo is formed as a result of double fertilization of the ovule, giving rise to two distinct structures; the zygote and primary endosperm nucleus giving rise to the plant embryo and the endosperm which together go on to develop into a seed.

(b) Construction of Genomic Library : The process of subdividing genomic DNA into clonable elements and inserting them into host cells is called creating a library.

A complete library, by definition, contains the entire genomic DNA of the source organism and is called as genomic library. A genomic library is a set of cloned fragments of genomic DNA. The process of creating a genomic library includes four steps :

In the first step the high molecular weight genomic DNA is separated and subjected to restriction enzy me digestion by using two compatible restriction enzymes.

In the second step, the fragments are then fractionated or separated by using agarose gel electrophoresis to obtain fragments of required size.

These fragments are then subjected to alkaline phosphatase treatment to remove the phosphate. In the third step, the dephosphorylated insert is ligated into vector which could be a plasmid, phage or cosmid, depending upon the interest of the researcher.

In the last step, the recombinant vector is introduced into the host by electroporation and amplified in host. In principle, all the DNA from the source organism is inserted into the host but this is not fully possible as some DNA sequences escape the cloning procedure. Genomic library is a source of genes and DNA sequences. A genomic library is a set of cloned fragments of genomic DNA. Prior information about the genome is not required for library construction for most organisms. In principle, the genomic DNA, after the isolation, is subjected to RE enzyme for digestion to
generate inserts.

cDNA libraries V/S Genomic libraries:

• Genomic library is a mixture of fragments of genomic DNA while cDNA obtained from mRNA may cloned to give rise to a cDNA library.Genomic library’ contains DNA fragments that represent genes as well as those that are not genes. In contrast cDNA library contains only those genes that are expressed in the concerned tissue/organism. In both cases, a mixture of fragments is used for cloning to establish the library.
• Use of cDNA is absolutely essential when the expression of an eukaryotic gene is required in a prokaryote.
• Eukaryotic cDNAs are free from intron sequences.
• As a result of the above, they are smaller in size than the corresponding genes, i.e., the genes that encoded them.
• A comparison of the cDNA sequence with the corresponding genome sequence permits the delineation of intron/exon boundaries.
• The contents of cDNA libraries from a single organism will vary widely depending on the developmental stage and the cell type used for preparation of the library. In contrast, the genomic libraries will remain essentially the same irrespective of the developmental stage and the cell type used.
• A cDNA library will be enriched for abundant mRNAs, but may contain only a few or no clones representing rare mRNAs.

(c) Alkaptonuria : This was one of the first metabolic diseases described by Garrod in 1908. It is an inherited metabolic disorder produced due to deficiency of an oxidase enzyme requiredfor breakdown ofhomogentisic acid (also called alcapton, hence, alkaptonuria is also written as alcaptonuria). Lack of the enzyme is due to the absence of the normal form of gene that controls the synthesis of the enzyme. Hence, homogentisic acid then accumulates in the tissues and is also excreted in the urine. The most commonly affected tissues are cartilages, capsules of joints, ligaments and tendons. The urine of these patients if allowed to stand for some hours in air, turns black due to oxidation of homogentisic acid.

Phenylketonuria (PKU; Foiling. 1934): It is an inborn metabolic disorder in which the homozygous recessive individual lacks the enzyme phenylalanine hydroxylase needed to change phenylalanine (amino acid) to tyrosine (amino acid). Thus, the biochemical abnormality in PKU is an inability to convert phenylalanine into tyrosine leading to hyperphenylalaninemia. Lack of the enzyme is due to the abnormal autosomal recessive gene on chromosome 12. This defective gene is due to substitution. Affected babies are normal at birth but within a few weeks there is rise (30-50 times) in plasma phenylalanine level which impairs brain development. Usually by six months of life severe mental retardation becomes evident.

If these children are not treated about one-third of these children are unable to walk and two-thirds cannot talk. Other symptoms are mental retardation, decreased pigmentation of hair and skin and eczema. Although large amounts of phenylalanine and its metabolites are excreted in the urine and sweat, yet it is believed that excess phenylalanine or its metabolites contribute to the brain damage in PKU. The heterozygous individuals are normal but carriers. It occurs in about 1 in 18000 births among white Europeans. It is very rare in other races.

Question 8.
(a) Give the step-wise procedure of Southern blotting technique. Mention any two important applications of this technique. [4]
(b) What are blunt ends and sticky ends ? How are they formed ? [4]
(c) Name any two industrial enzymes and give their uses. [2]
Answer:
(a) Southern blotting technique : In 1975, Edward M. Southern developed technique of DNA separation and its hybridization. Therefore, in his honor this technique is known as ‘ Southern blotting or Southern hybridization technique’. A specific DNA fragment can be separated and identified in a heterologous population of DNA molecules on the basis of binding of DNA probe with its complementary DNA strand.

The genomic DNA is isolated from the clone and digested with restriction enzymes. The DNA fragments are separated by agarose gel electrophoresis (Fig.). Different DNA bands are formed on agarose gel which represent DNA fragments of varying sizes. These fragments are transferred from gel to nylon or nitrocellulose membrane. The process of DNA transfer is called ‘blotting’.

A nitrocellulose membrane is put over the gel. Many layers of filter paper are placed over nitrocellulose membrane. This assembly is put in a container having NaOH solution. NaOH denatures DNA and results in formation of single stranded DNA. DNA fragments are transferred from gel to membrane by capillary action.

In addition, DNA fragments can also be transferred by vacuum blotting and centrifugation. The DNA fragments are fixed to membrane by using UV radiation or baking at 80°C. The pattern of DNA bands on membrane corresponds to the position of DNA on gel. The membrane is put in solution containing radio labelled DNA probe and incubated for some time. DNA probe hybridizes complementary DNA fragments fixed on membrane. It is gently washed at 12°C and dried.

The membrane is exposed through a photographic film. DNA bands formed on photographic film corresponds to the original position of DNA fragments present on agarose gel.

(b) Restriction enzymes are bacterial proteins that have the ability, to cut both the strands of the DNA molecule at a specific nucleotide sequence. There are hundreds of these restriction enzymes and each can cut the DNA at a specific point and the resulting DNA fragments are all of different lengths. Restriction enzymes can either produce sticky ends or blunt ends.

EcoRI enzyme binds to a region of having specific palindromic’ sequence (where two strands are identical when both are read in the same polarity i.e., in 5’→ 3’ direction). The length of this region is 6 base pairs i.e., hexanucleotide palindrome. It cuts between G and A residues of each strand and produces two single stranded complementary cut ends which are asymmetrical having 5’ overhangs of 4 nucleotides. These ends are called sticky ends or cohesive ends. Because nucleotide bases of this region can pair and stick the DNA fragments again as given below :}

On the other hand, there are some other Type II restriction enzymes which cleave both strands of DNA at the same base pairs but in the centre of recognition sequence, and results in DNA fragments with blunt ends or flush ends. For example Hae111 (isolated from Haemophilus aegypticus, the order of enzyme III), four nucleotide long palindromic sequence and cuts symmetrically the both DNA strands and forms blunt ends as below:

(c) Alpha Amylase : It is widely used enzyme in Food industry and in Laundry detergent.
Papain : It is used in Medicine, Food and Textile industries.

Question 9.
(a) Enlist the main steps in the regeneration of a complete plant from an explant. [4]
(b) Given below is a list of four bio molecules found in a living cell. For each of them, write the class of biomolecules they belong to and their location in a living cell: [4]
(i) Histones.
(iii) Haemoglobin.
(ii) mRNA.
(iv) Glycogen.
(c) Write any two uses of transgenic plants. [2]
Answer:
(a) Steps involved in in vitro regeneration of a complete plants. Regeneration refers to the development of organised structures like roots, shoots, flower buds, somatic embryos (SEs), etc. from cultured cells/tissues; the term organogenesis is also used to describe these events. Root regeneration occurs quite frequently but it is useful only in case of shoots and embryo germination. Only shoot and SE regenerations give rise to complete plants which is essential for applications of tissue culture technology in agriculture and horticulture. Regeneration may occur either directly from the explant or may follow an intervening callus phase.

Basic technique of Plant Tissue Culture: The basic technique of plant tissue culture involves the following steps:

• Preparation and sterilisation of suitable nutrient medium : Suitable nutrient medium as per objective of culture is prepared and transferred into suitable containers. Culture- medium is rich in sucrose, minerals, vitamins, and hormones. Yeast extract, coconut milk are also added. The culture is completely sterilized in an autoclave.
• Selection of explants : Selection of explants such as shoot tip should be done.
• Sterilisation of explants: Surface sterilisation of the explants by disinfectants (e.g., sodium hypochlorite or mercuric chloride) and then washing the explants with sterile distilled water is essential.
• Inoculation: Inoculation (transfer) of the explants into the suitable nutrient medium (which is sterilised by autoclaving to avoid microbial contamination) in culture vessels under sterile conditions is done.
• Incubations : Growing the culture in the growth chamber or plant tissue culture room, having the appropriate physical condition (i.e., artificial light: 16 hours of photoperiod), temperature (- 26°C) and relative humidity (50 – 60%) is required.
• Regeneration : An unorganized mass of cells developing from explants is called callus. The callus gives rise to embryoids which can develop into whole plant if the medium is provided with proper concentration of hormones. This property’ of developing every somatic cell into a Ml fledged plant is called totipotenev. Regeneration of plant, from cultured plant tissues is carried out.
• Hardening: Hardening is gradual exposure of plantlets to an environmental conditions.
• Plantlet transfer : After hardening, plantlets are transferred to the greenhouse or field conditions following acclimatization (hardening) of regenerated plants.

ISC Class 12 Biotechnology Previous Year Question Papers

ISC Biotechnology Previous Year Question Paper 2013 Solved for Class 12

Maximum Marks: 80
Time allowed: Three hours

• Candidates are allowed additional 15 minutes for only reading the paper. They must NOT start writing during this time.
• Answer Question 1 (Compulsory) from Part I and five questions from Part II, choosing two questions from Section A, two questions from Section B and one question from either Section A or Section B.
• The intended marks for questions or parts of questions are given in brackets [ ].
• Transactions should be recorded in the answer book.
• All calculations should be shown clearly.
• All working, including rough work, should be done on the same page as, and adjacent to the rest of the answer.

Part-1
(Answer all questions)

Question 1.
(a) Mention any one significant difference between each of the following : [5]
(i) Gene and Genome
(ii) Multi potent cell and Uni potent cell
(iii) Galactose and Glycine
(iv) Batch culture and Continuous culture
(v) Coding region and Non-coding region

(b) Answer the following questions : [5]
(i) Name the enzyme used in PCR. What is the source of this enzyme?
(ii) Why is Bt-cotton resistant to boll worm?
(iii) Mention any two methods of ex-situ conservation of germplasm.
(iv) What is Proteomics?
(v) Glucose and fructose have the same chemical formula (C₆H₁₂0₆), yet they differ in chemical properties. Why ?

(c) Write the Ml form of the following : [5]
(i) GDB
(ii) PIR
(iii) YAC
(iv) NCBI
(v) ddNTP

(d) Explain briefly : [5]
(i) Bacterial Artificial Chromosome
(ii) Vascular differentiation
(iii) Phenylketonuria
(iv) Quartemary protein
(v) Designer oils
Answer:
(a) (i) Gene: Gene is the unit of the genome, consisting of a sequence of DNA that occupies a specific position (locus) on a chromosome and determines a particular characteristic in an organism.

Genome: Genome is the total genetic information or all the genes contained in a haploid set of chromosomes in eukary otes, in a single chromosome in bacteria, or in the DNA or RNA of viruses.

(ii) Multipotent: These cells have the ability to differen-tiate into many of the various type of specialized cell types and can develop into any cell of a particular group or type. e.g., umbilical cord stem cells.

Unipotent: These cells can undergo unlimited reproductive divisions, but can only differentiate into a single type of cell or tissue, e.g., skin cells.

(iii) Galactose: It is a part of disaccharide that is made- up of two sugars. It is found in milk alongwith glucose. Galactose does not occur freely in nature. It is produced in the body during the digestion of disaccharide lactose.

Glycine: Glycine is a neutral amino acid and one of the 20 building blocks of protein. It is a non-essential amino acid, used in purine synthesis, and is a neurotrans¬mitter.

(iv) Batch culture: It is a type of culture in which nutrients are fed continously depending upon the amount consumed without removing growth products.

Continuous culture: It is a open type of culture in which nutrients are supplied from time to time alongwith removal of product in same volume.

(v) Coding region: Coding region (exon) is a part of the DNA that actually codes for a protein.

Non-coding region: Non-coding region (introns) is that part of DNA that does not code directly for a protein.

(b) (i) The enzyme used in PCR is TAQ – DNA polymerase I and the source of this enzyme is Thermus aquaticus.

(ii) Bt-co.tton is an insect-resistant Genetically Modified (GM) variety of cotton seed, which contains a cry gene from Bacillus thuringiensis to kill the bollworm.

(iii) Ex-situ conservation of germplasm refers to maintaining or conserving the germplasm of organism outside their natural seed habitats. Two methods of ex-situ germplasm conservation are seed banks, botanical gardens, zoological parks etc.

(iv) Proteomics is the study of entire complement of proteins, particularly their structures and functions on the large scale. The term “proteomics” was first coined in 1997 and used to make an analog}’ with genomics, the study of the genes. The word “proteome” is derived from “protein’ and “genome”, and this was coined by Marc Wilkins in 1994. It is constantly changing due to intracellular and extracellular factors.

(v) Both Glucose and fructose have the same chemical formula, but they are different because of the different arrangement of the atoms within the molecules. Glucose is an aldose with a -CHO group at position 1 while fructose is a ketose with a -C = O at position 2.

(c) (i) Genome Data Base

(ii) Protein Information Resource

(iii) Yeast Artificial Chromosome.

(iv) National Centre for Biotechnolog} Information

(v) Dideoxynucleoside triphosphate.

(d) (i) Bacterial artificial chromosome (B AC) is a cloning l ector construct, based on a fertility plasmid (or F-plasmid). which is used for transforming and cloning in bacteria, usually E.coli. An ori gene for maintainance of F factor, a selectable marker and many restriction sites for insertion of foreign DNA. The bacterial artificial chromosome’s usual insert size is 300 to 350 kbp.

(ii) Vascular tissues are complex tissues, each consisting of a number of different types of cells. Vascular differentiation refers to the process by which different types cell types arise from precursor cells and become different in structure and function from each other.

(iii) Phenylketonuria is the recessive genetic disorder caused by the absence of the enzyme phenylalanine hydroxylase which catalyzes the conversion of phenylpyruvic acid into hydroxyphcnyl pyruvic acid. It is caused due to mutation of gene.

(iv) Quartemary proteins are the multimeric proteins i.e.. proteins hav ing more than two or more polypeptide chains which are linked to form quartemary structure, e.g.. Haemoglobin.

(v) Designer Oil: “Designer oil” that reduces LDL (‘bad“) blood cholesterol levels in humans and increases energy expenditure which may prevent people from gaining weight. The oil incorporates a phytosterol-based functional food ingredient Phytrol (TM) from Forbes into oil using proprietary technology.

Part-II
(Answer any five questions)

Question 2.
(a) Give a comparative account of DNA and RNA on the basis of their following characteristics: [4]
(i) Chemical composition and structure
(ii) Location and function
(b) Mention the uses of the following in genetic engineering techniques : [4]
(i) Shuttle vectors and Expression vectors
(ii) Restriction endonucleases
(c) What is electroporation ? [2]
Answer:
(a) (i) DNA:

• DNA has 2-Deoxyribose sugar.
• It contains cytosine and thymine as pyrimidine.
• It has a double stranded helix struc-ture.

RNA:

• RNA has ribose sugar.
• It contains cytosine and uracil as pyrimidine.
• It has a single stranded helix.

(ii) DNA:

• DNA occurs in the nucleus chloroplast and mitochondria of cell.
• It controls transmission of hereditary characters.

RNA:

• RNA occurs in cytoplasm of the cell.
• It controls the synthesis of proteins.

(b) (i) Shuttle vectors exist and work and allow DNA to be transferred between both prokaryotes and eukaryotes. The shuttle vector has two origins of replication i.e.. on^E and ori^Euk allowing replication to occur in either system/host. It “shuttles” between two different species. It can be used to perform reverse genetics, e.g.. Yeast episomal plasmid (YEP). Expression vectors allow expressing certain genes directly from their recombinant DNAs A typical expression vector will have a promoter upstream of the DNA containing the sequence to be expressed.

(ii) Restriction endonucleases are enzymes that cleave DNA at specific nucleotide sequences. The sequence recognized is often four to six nucleotides long. For example, the restriction endonucleases Eco RI recognize the sequence. GAATTC.

(c) Electroporation is a mechanical method used to introduce polar molecules into a host cell through the cell membrane. In this procedure, a brief exposure to a high electric voltage pulse temporarily disturbs the phospholipid bilayer, allowing introduction of molecules like DNA to pass into the cell.

Question 3.
(a) What is gene cloning ? Mention the steps involved in this process
(b) Explain the following :
(i) Acidic and basic amino acids
(ii) Phospholipids and glycolipids
(c) State any four objectives of germplasm conservation.
Answer:
(a) The process of formation of similar copies of a desired gene is called gene cloning. Gene cloning is the technique of recombinant DNA technology’ in which a desired gene of interest having a characteristic feature is cloned. Gene cloning involves the replication of DNA fragments by the use of self-replicating vector’s genetic material for its multiplication, expression or integration into host chromosome.

Steps involved in gene cloning :

• In cloning a gene the first step is to isolate the DNA segment from the organism that contains the gene of interest.
• Remove the gene of interest from the DNA, by using restriction enzymes or by PCR.
• Vector is also treated with same restriction enzyme, to cleave it. Vector come to possessing single strand at the ends called stick}’ ends.
• Then the enzy me DNA ligase is used to insert the gene of interest to be cloned into the plasmid. Vector having sicky ends to form recombinant DNA.
• The plasmid or vector acts as a vehicle that transports the desired gene into a host cell, the process is known as transformation.
• Now, these recombinant plasmids are inserted into bacterial host cells, where they replicate to amplify the desired gene, the process is called gene cloning.
• Now the cell can be plated out on an agar medium. The colony of cells containing the desired cloned gene can be identified and isolated.

(b) (i) Amino acids are the basic structural unit of all proteins. A free’ neutral amino acid (a single amino acid) always has an amino group -NH₂. a carboxyl group -COOH, hydrogen -H and a chemical group or side chain -”R”.

Acidic amino acid :
Two amino acids have acidic side chains at neutral pH. These are aspartic acid or aspartate (Asp) and glutamic acid or glutamate (Glu). Their side chains have carboxylic acid groups whose pKa’s are low enough to lose protons, becoming negatively charged in the process. Such amino acids are highly polar.

Basic amino acid :
Three amino acids have three basic side chains at neutral pH. These are arginine (Arg), lysine (Lys). and histidine (His). Their side chains contain nitrogen and resemble ammonia, which is a base. Their pKa’s are high enough that they tend to bind protons, gaining a positive charge in the process.

(ii) Phospholipids are the phosphorylated triglyceride lipids in which one fatty acid is replaced by phosphate group added by phosphorylation. Glvcolipids are the glycosylated lipids in which sugar residue galactose or carbohydrate molecule is added by glycosylation. Phospholipids and glycolipids both are the derivatives of lipids. They form an essential component of cell membrane which plays a role in structure, maintenance and also help in eliciting certain immune reactions.

(c) Objectives of Germplasm Conservation :

• Conservation of rare germplasm arising through somatic hybridization.
• Storage of pollen for enhancing longevity.
• Maintainance of recalcitrant seeds.
• To develop genes for adaptations / endurance to varying, unfavorable biotic/abiotic stresses / environments.
• To develop high yielding varieties.

Question 4.
(a) Why are enzymes temperature sensitive ? Briefly explain the mode of action of enzymes on their substrate. [4]
(b) How is the hormone insulin synthesized, using genetic engineering technique ? State two ways in which this technique is better than the techniques used earlier. [4]
(c) What is a supra-molecular assembly ? [2]
Answer:
(a) Enzymes are temperature sensitive because almost all enzymes are proteins have tertiary structure and only function in a specific range of temperature. Exposing enzymes to high temperature break bonds and can cause them to denature, which alter the shape of the enzyme. Due to change in shape the substrate no longer ‘fits’ inactive site of the enzyme and can no longer function as normal.

Mode of enzyme action : It can be explained by this models :

Lock and key mechanism : This model was proposed by Emil Fisher in 1898. It is also called the template model. According to this model the union of the substrate and the enzyme takes place at the active site, more or less in a manner in which a key fits in a lock and results in formation of an enzyme substrate complex. As the two molecules are involved, this hypothesis is also known as the concept of inter molecular fit. The ES complex is highly unstable and almost immediately this complex breaks to produce the end product of the reaction and regenerate the free enzyme. The ES complex results in the release of energy.

Examples:
Catalase : It catalyzes the decomposition of hydrogen peroxide into water and oxygen.
2H₂O₂ → 2H₂O + O₂
One molecule of catalyses can break 40 million molecules of hydrogen peroxide each second.

The first major medicinal product of genetic engineering is human insulin called Humulin. Insulin is a protein that acts as a hormone to stimulate uptake of blood sugar into tissues, such as the liver and the muscles.
Following are the steps which are involved in insulin synthesis :

• Isolate the gene responsible for producing human insulin protein. The gene is a part of the DNA in a human chromosome.
• Then remove a circular piece of DNA called plasmid from a bacterial cell. Special restriction enzymes are used to cut the plasmid ring open with sticky ends.
• With the plasmid ring open, the gene for insulin is inserted into the plasmid ring and the ring is closed with ligase enzyme forming recombinant DNA. This process is called recombinant technology’.
• The bacterial plasmid DNA now contains the human insulin gene and is inserted into a bacteria.
• Many plasmids with the insulin gene are inserted into many bacterial cells. When the bacterial cells reproduce by dividing, the human insulin gene is also cloned in the newly cloned cells.
• Human insulin protein molecules produced by bacteria are gathered and purified by down stream process by culturing the genetically engineered bacteria, limitless supplies of insulin may be produced.

Two ways in which genetic engineering is better than the technique used earlier:

• Insulin produced by genetic engineering is pure and has no allergic reaction.
• The human insulin is much cheaper when produced by r-DNA technology than was the insulin from cows, as it could be produced much more quickly in greater quantity.

(c) A supra molecular assembly or “super molecule” is a well defined complex of molecules held together by non-covalent bonds. Molecules are combined in the form of sphere or rod. The dimensions of supra molecular assemblies can range from nanometres to micrometers. The process by which a supra molecular assembly forms is called molecular self-assembly.

Question 5.
(a) What is plant tissue culture ? Discuss the organization of a tissue culture laboratory under the following headings: [4]
(i) Media preparation
(ii) Culture room.
(b) Explain any two methods used for the identification of recombinant host cells from the non-recombinant host cells. [4]
(c) Name any four in vivo techniques employed in haploid production. [2]
Answer:
(a) Plant tissue culture is the technique of in vitro maintenance and growth of plant cells, tissues and organs under aseptic conditions on a suitable artificial culture medium contained in small containers under controlled environmental conditions of temperature and light.

(i) Media Preparation Room : An area is required for preparation of media. In such space there should be provision for bench space for chemicals, labware, culture vessels, closures and miscellaneous equipment required for media preparation and dispensing. In this room provision is also made for placing hot plates or stirrers, pH meter, balance, waterbath, burners, oven, autoclave, culture vessel, refrigerator etc.

(ii) Culture Room : All types of cultured plant tissues are incubated under the conditions of well controlled temperature, humidity, illumination and air circulation. The culture room should have light and temperature control system. Generally temperature is maintained at 25±2°C and 20-98% relative humidity and uniform air ventilation. The cultures are grown in diffused light and darkness each for a period of 12 hours.

(b) The introduction of the recombinant DNA in to a suitable host cell is followed by the selection of those cells, which contain the recombinant vectors. There are various selection methods that are based on the expression or non-expression of some of the traits present in the vector or alongwith the cloned gene.

Antibiotic sensitivity : Recombinant plasmid has many traits such as ori recognition site and selectable marker gene. Some of these traits are resistant to certain antibiotics. If the antibiotic resistant gene is present alongwith the cloned gene, it is very easy to select the recombinant transformants directly on a medium supplemented with respective antibiotic.

In most of the cases there are two stages of selection. First is the selection on the basis of . transformed cells i.e., the cells that have taken a plasmid. The second one is to identify the transformed cells that have the recombinant plasmid. The presence of a desired DNA insert can be confirmed either by isolating the recombinant plasmids and digesting it with the same restriction enzyme used for making the recombinant vectors, by PCR, by southern hybridisation with DNA probes, by northern hybridisation with RNA probes and by direct DNA sequencing

lnsertional inactivation : Another method to differentiate between recombinant and non¬recombinant is on the basis of their ability to produce colour.
lnsertional inactivation: In this method, a recombinant DNA is within the coding sequence of an enzyme p-galactosidase. This results into the inactivation of enzyme which is referred to as insertional inactivation.

The bacterial colonies whose plasmids do not have insert, produce blue colour but those with an insert or the recombinant do not produce any colour and are identified as recombinant colonies.

(c) In vivo techniques employed in haploid production are gynogenesis, ovule and rogenesis, genome elimination by distant hybridisation or chemical treatment and semigamy.

Question 6.
(a) Write the principle and any two applications of each of the following biochemical techniques : [4]
(i) Ion – exchange chromatography
(ii) Gel – permeation
(b) What is a genetic code ? Enlist three important properties of genetic code. [4]
(c) What are DNA probes ? [2]
Answer:
(b) (i) Principle of Ion-exchange chromatography : It is defined as the reversible exchange of ions in solution with ions electrostatically bound to some sort of insoluble support medium. Separation is obtained since different molecules have different degree of interaction with the ion-exchanger due to difference in their charges, charge densities and distribution of charge on their surfaces. These interactions can be controlled by varying conditions such as ionic strength and pH.

An ion-exchanger consists of an insoluble matrix to which charged groups have been covalently bound. Ion exchange separations are carried out mainly in columns packed with an ion-exchanger. There are two types of ion-exchanger, namely cation and anion exchangers. Cation exchangers possess negatively charged groups and these will attract positively charged cations. Anion exchangers have positively charged groups that will attract negatively charged anions. After the ion exchange the molecules can be eluted from the matrix by selective desorption. The selective desorption can be achieved by changes in pH and /or ionic concentration or by affinity elution, in which case an ion that has greater affinity for the exchange than has the bound ion is introduced into the system.

Applications:

• Polystyrene and polyphenolic ion exchange resins are more often used to separate srhall molecule such as amino acids, small peptides, nucleotides, N-bases, cyclic nucleotides, organic acids.
• The cellulose ion exchangers are commonly used for proteins, including enzymes, polysaccharides and nucleic acids.

Principle of Gel-permeation chromatography: Gel permeation / filtration chromatography is a separation technique which uses molecular sieves, composed of neutral cross-linked carriers e.g., polymers like agarose, dextrans of different pore sizes. Therefore, it can separate macromolecule of different sizes from one another. Molecules smaller than pore size either the carrier and are retained. They are later eluded (in order of molecular size) and collected. Other names that have been suggested for this technique are : get filtration, molecular or size exclusion chromatography ; or molecular sieve chromatography.

Applications:

• Separation of polysaccharide, enzymes, antibodies and other proteins.
• Separation of non-polar species such as triglycerides in non-aqueous mobile phases.
• Used to analyse the molecular-weight distribution of organic soluble polymer.

The genetic code is called a triplet code, i.e sequence of three nitrogenous bases on m-RNA that specifies the recognition of a particular of a single amino acid. Thus, the information encoded in the sequence of nitrogenous bases must be read in groups of three, (UAC, GGC, UGC).

Three important properties:

1. Triplet code : Three adjacent nitrogen bases constitute a codon which specifies the placement of one amino acid in a polypeptide.
2. Start signal : Polypeptide synthesis is signaled by AUG or methionine codon and GUG — Valine codon. They have dual function.
3. Stop signal: Polypeptide chain termination is signaled by three termination codons — UAA, UAG, and UGA. They do not specify any amino acid and are hence also called non-sense codon.
4. Universal code : The genetic code is applicable universally i.e., the codon specifies the same amino acid from a virus to a tree or human being.
5. Non-ambiguous codon : One codon specifies only one amino acid and not any other.

(c) DNA Probe : It is a solution of radioactive, single-stranded DNA or oligodeoxy nucleotides (a DNA segment of few to several nucleotides). The name probe signifies the fact that this DNA molecule is used to detect and identify the DNA fragment in the gel/membrane that has a sequence complementary to the probe. The probe hybridises with the complementary DNA on the membrane to the greater extent with a low non-specific binding on the membrane. This step is known as hybridisation reaction.

Question 7.
(a) How can the following plants be obtained, using genetic transformation techniques . [4]
(i) Drought and salinity tolerant plants
(ii) Somatic hybrids
(b) Explain the process involved in the transcription of DNA to mRNA. Also, mention any two post transcriptional changes that occur in the mRNA formed. [4]
(c) What are Okazaki fragments ? How are they joined ? [2]
Answer:
(i) Drought tolerance : Water is crucial for all living things. Plants use water as a solvent, a transport medium, an evaporative coolant, physical support, and as a major ingredient for photosynthesis. Without sufficient water, agriculture is impossible. Therefore, drought tolerance is an extremely important agricultural trait.

One way of engineering drought tolerance is by taking genes from plants that are naturally drought tolerant and introducing them to crops. The resurrection plant (Xerophyta viscosa), a native of dry regions of southernmost Africa, possesses a gene for a unique protein in its cell membrane. Experiments have shown that plants given this gene are less prone to stress from drought and excess salinity.

Some genes have been found that control the production of the thin, protective cuticle found on leaves. If crops can be grown with a thickened waxy cuticle, they could be better equipped for dealing with dryness.

Salt tolerance: Irrigation has enabled the transformation of arid regions into some of the world’s most productive agricultural areas. Excess salinity, however, is becoming a major problem for agriculture in dry parts of the world. In several cases, scientists have used biotechnology to develop plants with enhanced tolerance to salty conditions.

Researchers have noticed that plants with high tolerance to salt stress possess naturally high levels of a substance called glycine betaine. Further, plants with intermediate levels of salinity tolerance have intermediate levels, and plants with poor tolerance to salinity have little or none at all. Genetically modified tomatoes with enhanced glycinebetaine production have increased . tolerance to salty conditions.

Another approach to engineering salt tolerance uses a protein that takes excess sodium and diverts it into a cellular compartment where it does not harm the cell. In the lab, this strategy was used to create test plants that were able to flower and produce seeds under extreme salt levels. Commercially available crops with such a modification are still several years away.

(ii) Process, other than the sexual cycle has recently become available for higher plants, which can lead to genetic recombination. This non-conventional genetic procedure involving fusion between isolated somatic protoplasts under in vitro conditions and subsequent development of their product (heterokaryon) to a hybrid plant is known as somatic hybridisation.

Application of Somatic Hybridisation :

• Somatic cell fusion appears to be the only means through w hich two different parental genomes can be recombined among plants that cannot reproduce sexually (asexual or sterile).
• Protoplasts of sexually sterile (haploid, triploid, and aneuploid) plants can be fused to produce fertile diploids and polyploids.
• Somatic cell fusion overcomes sexual incompatibility barriers. In some cases, somatic hybrids between two incompatible plants have also found application in industry or agriculture.
• Somatic cell fusion is useful in the study of cytoplasmic genes and their activities and this information can be applied in plant-breeding experiments.

(b) The process of transcription: Transcription is the process of creating a messenger RNA strand from DNA, performed by the enzyme RNA polymerase, Transcription always occurs in a 5′ → 3′. direction, with polymerase moving 3′ → 5′ along the DNA strand.

Transcription Initiation : There are three steps in transcription :
Initiation : RNA synthesis begins after the RNA polymerase attaches to the DNA and unwinds it. RNA synthesis will always occur on the template strand.

Elongation : RNA polymerase unwinds the DNA double helix and moves downstream and elongates the RNA transcript by adding ribonucleotides in a 5′ → 3′ direction. Each ribonucleotide is added to the growing mRNA strand using the base pairing rules (A binds with T, G binds with C). For each C encountered on the DNA strand a G is inserted in the RNA, for each Q a C and for each T, an A is inserted. Since there is no T in RNA, U is inserted whenever an A is encountered. After RNA polymerase has passed, the DNA restores its double stranded structure.

Termination: When the mRNA is complete, the mRNA is released and the RNA polymerase releases from the DNA.

Two post transcriptional changes that occur in the mRNA formed are:
RNA transcripts eukaryotes are modified or processed, before leaving the nucleus to produce functional wRNA. It is processed in two ways :
(1) 5 ‘ capping : Capping of the pre-mRNA involves the addition of 7-methylguanosine (m7G) to the 5′ end.,
(2) 3′ polyadenylation: The pre-mRNA processing at the 3′ end of the RNA molecule involves cleavage of its 3′ end and then the addition of about 200 adenine residues to form a poly (A) tail. The cleavage and adenylation reactions occur if a polyadenylation signal sequence (5′ – AAUAAA-3′) is located near the 3′ end of the pre-mRNA molecule, followed by another sequence, which is usually (5′ -CCA-3’).

(c) Okazaki fragments are short, newly synthesized DNA fragments produced discontinously in pieces during DNA replication. They are formed on the lagging template strand and are complementary to the lagging template strand. Okazaki fragments are joined together by DNA ligase enzyme.

Question 8.
(a) What is meant by the term genomics ? Write the differences between structural genomics and functional genomics. [4]
(b) Name and explain any four methods of synchronization of cells. [4]
(c) What is meant by Expressed sequence tags ? [2]
Answer:
(a) The word ‘genomics’ has taken root from the term ‘genome’ which is an organism’s total genetic constitution mapping, sequencing and analyzing the genomic information to solve a medical, industrial or biological query. Genomics studies investigate structure and function of genes and do this simultaneously for all the genes in a genome. Genomics is broadly categorized into structural and functional genomics.

Structural Genomics : The structural genomics deals with DNA sequencing, sequence assembly, sequence organisation and management. Basically it is the starting stage of genome analysis i.e,. construction of genetic, physical or sequence maps of high resolution of the organism. The complete DNA sequence of an organism is its ultimate physical map. Due to rapid advancement in DNA technology and completion of several genome sequencing projects for the last few years, the concept of structural genomics has come to a state of transition. Now it also includes systematics and determination of 3D structure of proteins found in living cells. Because proteins in every group of individuals vary and so there would also be variations in genome sequences.

Functional Genomics: It is based on the information of structural genomics the next step is to reconstruct genome sequences and to find out the function that the genes do. This information also lends support to design experiment to find out the functions that specific genome does. The strategy of functional genomics has widened the scope of biological investigations. This strategy is based on systematic study of single gene / protein to all genes/proteins.

Therefore, the large scale experimental methodologies (along with statistically analysed / computed results) characterise the functional genomics. Hence, the functional genomics provide the novel information about the genome. This eases the understanding of genes and function of proteins, and protein interactions.

(b) Cell culture synchronization : Cells in suspension cultures vary greatly in size, shape, DNA, and nuclear content. Moreover, the cell cycle time varies considerably within individual cells. Therefore, cell cultures are mostly asynchronous.

It is essential to manipulate the growth conditions of an asynchronous culture in order to achieve a higher degree of synchronization. A synchronous culture is one in which the majority of cells proceed through each cell cycle phase (G1: S, G2 and M) simultaneously.

Synchronization can be achieved by following methods :

• Physical methods include selection by volume (size of cell aggregate.)
• Chemical methods include starvation (depriving suspension cultures of an essential growth compound and culture supplying).
• Chemical methods include inhibition (temporarily blocking the progression of events in the cell cycle using a biochemical inhibitor and then releasing the block).

(c) An Expressed Sequence Tag or EST is a short sub-sequence of a transcribed cDNA sequence represents a partial gene. They may be used to identify gene transcripts, and are instrumental in gene discovery and gene sequence determination, used in micro-arrays.

Question 9. .
(a) What is Human Genome Project ? Mention its objectives and significant achievements. [4]
(b) Write short notes on : [4]
(i) Locus – link
(ii) Microprocessor
(iii) EMBL
(iv) Taxonomy Browser
(c) What is site-directed mutagenesis ? [2]
Answer:
(a) The Human Genome Project (HGP) : This is an international scientific research project with a primary goal to determine the sequence of chemical base pairs which make-up DNA and to identify the approximately 25,000 genes of the human genome from both a physical and functional standpoint.

Benefits: The work on interpretation of genome data is still in its initial stages. It is anticipated that detailed knowledge of the human genome will provide new avenues for advances in medicine and biotechnology. A number of companies, such as Myriad Genetics started offering easy ways to administer genetic tests to a variety of illnesses, including breast cancer, disorders of homeostasis, cystic fibrosis, liver diseases and many others. Also, the etiologies for cancers, Alzheimer’s disease and other areas of clinical interest are considered likely to benefit from genome information and possibly may lead in the long term to significant advances in their management.

There are also many tangible benefits for biological scientists. For example, a researcher investigating a certain form of cancer may have narrowed down his/her search to a particular gene. By visiting the human genome database on the world wide web, this research can examine what other scientists have written about this gene, including (potentially) the three-dimensional structure of its product, its function(s), its evolutionaty relationships to other human genes, or to genes in mice or yeast or fruit flies, possible detrimental mutations, interactions with other genes, body tissues in which this gene is activated, diseases associated with this gene or other data types.

(b) Locus Link is a National Center for Biotechnology Information (NCBI) online resource. It is designed to link together related information on genetic loci and gene products from several sources.

Microprocessor : A microprocessor or processor is the heart of the computer and it performs all the computational tasks, calculations and data processing etc. inside the computer. Microprocessor is the brain of the computer. In the computers, the most popular type of the processor is the Intel Pentium chip and the Pentium IV is the latest chip by Intel Corporation. The microprocessors can be classified based on the following features.
Instruction Set: It is the set of the instructions that the Microprocessor can execute.
Bandwidth : The number of bits processed by the processor in a single instruction.
Clock Speed : Clock speed is measured in the MHz and it determines that how many instructions a processor can processed.

European Molecular Biology Laboratory (EMBL) : It was established to collect, organise and distribute data on nucleotide sequence and other information rebated to them. Nucleotide Sequence Database (also known as EMBL -Bank) constitutes Europe’s primary nucleotide sequence resource. Main sources for DNA and RNA sequences are direct submission from individual researches, genome sequencing projects and patent applications.

Taxonomy Browser: This search tool provides taxonomic information on various species. The Taxonomy database of NCBI has information (including scientific and common names) about all organisms for which some sequence information is available (over 79,000 species). The server provides genetic information and the taxonomic relationship of the species in question. Taxonomy has links with other servers of NCBI e.g., structure and PubMed.

(c) Site-directed mutagenesis is a molecular biology technique in which a mutation is created at a specific site in the DNA molecule.

ISC Class 12 Biotechnology Previous Year Question Papers