Microbiology with Diseases by Taxonomy Chapter 7 Answers 1CM<\/strong><\/span>
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\n<\/p>\nMicrobiology with Diseases by Taxonomy Chapter 7 Answers 1CT<\/strong><\/span>
\nDNA of nucleotides used as template for replication and transcription, with radioactive deoxyribose as template:<\/strong>
\nExplanation<\/strong>
\nDeoxyribonucleic acid (DNA) encodes genetic instructions in all living organisms. It is a nucleic acid, composed of major macro molecules, containing double-stranded helices. It organized into long structures known as chromosomes. Moreover, it is used in genetic engineering, forensics, bioinformatics, and DNA nanotechnology.
\nSimilarly, ribonucleic acid (RNA) is a biological molecule, which plays an important role in coding, decoding regulation, and expression of genes. However, it is usually single-stranded and plays an important role in the cells by catalyzing reactions.
\nThe percentage of DNA and RNA strands that are radioactive after DNA replication are:<\/strong>
\nExplanation<\/strong>
\nAfter completion of DNA replication cycles, DNA strand contain 12.5 % of radioactive sugars. Therefore, in RNA molecules do not contain radioactive sugars, because it uses only ribose sugar, whereas in experiment only deoxyribose is radioactive.<\/p>\nMicrobiology with Diseases by Taxonomy Chapter 7 Answers 1FB<\/strong><\/span>
\nThe three steps in RNA transcription are initiation<\/strong>, elongation<\/strong>, and termination<\/strong>.
\nCells first make an RNA (ribonucleic acid) copy of the gene; this process is known as transcription. In RNA transcription three steps are involved, they are initiation of transcription, elongation, and termination.
\nRNA polymerase is an enzyme, which produces RNA. It attaches to the promoters (specific nucleotide sequences) that is located in the beginning of the gene and initiates the transcription. It transcribes the DNA template in to RNA. RNA is produced in 5\u2019-3\u2019 direction.
\nIn elongation, RNA polymerase moves down the DNA template to synthesize RNA.
\nFinally RNA polymerase falls off on the 5\u2019 end of the DNA template. It leads to the termination of the transcription.
\nHence, the correct answers are initiation<\/strong>, elongation<\/strong>, and termination<\/strong>.<\/p>\nMicrobiology with Diseases by Taxonomy Chapter 7 Answers 1L<\/strong><\/span>
\nThe given diagram is showing the discontinuous synthesis of a lagging strand during DNA replication.
\nThe parts a, b, c, d, e, f, g, h, i, j, k and l can be identified as listed below:
\na. Replication fork: <\/strong>
\nIt is the spot at which both strands of DNA get separated to allow replication of individual strands.
\nb. Stabilising proteins:<\/strong>
\nThey help in unwinding and parting of the two strands of the DNA molecule.
\nc. Nucleotide trisphosphate:<\/strong>
\nThese are the main components of nucleic acids. They not only provide energy but also give phosphate groups during phosphorylation reactions.
\nd. Leading strand:<\/strong>
\nThis is strand produced in continuation in 5\u2019 to 3\u2019 direction due to polymerization.
\ne. Helicase (enzyme):<\/strong>
\nIt is an enzyme which is responsible for separation of double helical strands of DNA.
\nf. Primase (enzyme):<\/strong>
\nIt is the enzyme that builds short RNA molecules complementary to the DNA template.
\ng. DNA polymerase III (enzyme):<\/strong>
\nThis is the enzyme involved in the proof reading function when nucleotides are being added to the new strand.
\nh. RNA primer:<\/strong>
\nIt is a small strand composed of nucleic acids and is the starting point to begin DNA synthesis.
\ni. Okazaki fragments:<\/strong>
\nThe short segments of DNA on the lagging strand during replication. These are joined as one by an enzyme ligase.
\nj. DNA polymerase I (enzyme):<\/strong>
\nIt is the enzyme which removes the RNA primer. RNA primer is replaced by the DNA. It also plugs in the required nucleotides amid the Okazaki fragments.
\nk. Lagging strand: <\/strong>
\nThe newly formed discontinuous strand opposite to replication fork in leading strand in 3\u2019 \u2013 5\u2019 direction.
\nl. Ligase (enzyme):<\/strong>
\nThis enzyme is responsible for filling the gaps in sugar phosphate back bone of the DNA. It also helps in joining the Okazaki fragments.<\/p>\nMicrobiology with Diseases by Taxonomy Chapter 7 Answers 1MC<\/strong><\/span>
\nAn organized structure of DNA (deoxyribonucleic acid), protein and RNA (ribonucleic acid) found in cells is known as chromosome. It contains DNA-bound proteins which serve packaging the DNA and controls it functions.
\na) 4,000,000 base pairs:<\/strong>
\nEach cell contains more than one type of chromosome. Chromosomes are existed as either duplicated (two identical copies) or unduplicated (single duplicated strands).
\nIn eukaryotes linear chromosome is present whereas in prokaryotes small circular chromosome is present.
\nIn eukaryotes chromosomes are packed by proteins into a condensed structure is known as chromatin. In bacterial chromosomes the 4,000,000 base pairs are present. Hence, this option is correct.
\nb) 4000 base pairs:<\/strong>
\nEach cell contains more than one type of chromosome. Chromosomes are existed as either duplicated (two identical copies) or unduplicated (single duplicated strands).
\nIn eukaryotes linear chromosome is present whereas in prokaryotes small circular chromosome is present.
\nIn eukaryotes chromosomes are packed by proteins into a condensed structure is known as chromatin. In bacterial chromosomes the 4,000,000 base pairs are present. Hence, this option is incorrect.
\nc) 400 base pairs:<\/strong>
\nEach cell contains more than one type of chromosome. Chromosomes are existed as either duplicated (two identical copies) or unduplicated (single duplicated strands).
\nIn eukaryotes linear chromosome is present whereas in prokaryotes small circular chromosome is present.
\nIn eukaryotes chromosomes are packed by proteins into a condensed structure is known as chromatin. In bacterial chromosomes the 4,000,000 base pairs are present. Hence, this option is incorrect.
\nd) 40 base pairs:<\/strong>
\nEach cell contains more than one type of chromosome. Chromosomes are existed as either duplicated (two identical copies) or unduplicated (single duplicated strands).
\nIn eukaryotes linear chromosome is present whereas in prokaryotes small circular chromosome is present.
\nIn eukaryotes chromosomes are packed by proteins into a condensed structure is known as chromatin. In bacterial chromosomes the 4,000,000 base pairs are present. Hence, this option is incorrect.
\nHence, the correct option is (a) 4,000,000 base pairs <\/strong>which is the present in the bacterial chromosome.<\/p>\nMicrobiology with Diseases by Taxonomy Chapter 7 Answers 1SA<\/strong><\/span>
\nGenotype of bacterium determines its phenotype:<\/strong>
\nExplanation<\/strong>
\nSet of genes in the genome is known as genotype of an organism. Physical features and function traits of an organism is known as phenotype. Examples are antibiotic resistance, morphology, structure, and metabolism. Moreover, it is mainly used in determining the difference in genetic makeup of an individual by observing the DNA sequence of biological assays.
\nThe following methods of genotyping, which includes are:<\/strong><\/p>\n\n- Restriction fragment length polymorphism identification (RFLPI).<\/li>\n
- Amplified fragment length polymorphism detection (AFLPD).<\/li>\n
- Random amplified polymorphic detection (RAPD).<\/li>\n
- DNA sequencing.<\/li>\n
- Polymerase chain reaction (PCR).<\/li>\n
- Allele specific oligonucleotide (ASO).<\/li>\n<\/ol>\n
Similarly, genotype of bacteria is encoded by gene in DNA, which is transcribed into mRNA. The mRNA is translated into protein (polypeptide). In this translation, ribosomes play an important role.
\nThus, a bacterium contains different genotypes with different proteins and determines different phenotype.<\/p>\n
Microbiology with Diseases by Taxonomy Chapter 7 Answers 2CT<\/strong><\/span>
\nThe amino acid sequences in polypeptide are synthesized by eukaryotic ribosomes:<\/strong>
\nExplanation<\/strong><\/p>\n\n- Messenger RNA is large family of molecules. They transmit genetic information to DNA and to ribosome.
\nTranscription of mRNA is followed by the RNA polymerase, and then it translated to polymers of amino acids and proteins.<\/li>\n - In DNA mRNA genetic information is determined in nucleotide sequence.<\/li>\n
- If mRNA have the nucleotide base sequences, then sequence of amino acids in polypeptides are synthesized by eukaryotic ribosomes.<\/li>\n<\/ol>\n
The sequence of amino acids in polypeptides is synthesized by eukaryotic ribosomes by the following below.<\/p>\n
\n- AUGGGGAUACGCUACCCC
\nMet-Gly-Ile-Arg-Tyr-Pro<\/li>\n - CCGUACAUGCUAAUCCCU
\nPro-Tyr-Met-Leu-Ile-Pro<\/li>\n - CCGAUGUAACCUCGAUCC
\nPro-Met (stop)<\/li>\n - AUGCGGUCAGCCCCGUGA
\nMet-Arg-Ser-Ala-Pro (stop<\/li>\n<\/ul>\nMicrobiology with Diseases by Taxonomy Chapter 7 Answers 2FB<\/strong><\/span>
\nA triplet nucleotide sequence that specifies a particular amino acid is known as codon<\/strong>.
\nThe mRNA (messenger RNA) is large family of the RNA and it transmits genetic information from DNA (deoxyribonucleic acid) to the ribosome.
\nIt mainly involves in transcription, transport and translation. Important function of mRNA carries genetic information.
\nGenetic codon is a set of rules by which the information stored in DNA or RNA is translated into proteins. Generally the codon is a sequence of three nucleotides called triplet. Each triplet specifies one amino acid during protein synthesis.
\nHence, the correct answer is codon<\/strong>.<\/p>\nMicrobiology with Diseases by Taxonomy Chapter 7 Answers 2MC<\/strong><\/span>
\nProkaryotic chromosomes are circular and they are present in the cytosol.
\na) They typically have two or three origins of replication:<\/strong>
\nIn prokaryotes genome is made by the plasmid and chromosome. They contain only one chromosome.
\nThey contain circular chromosome and introns are absent. In prokaryotes nucleus is absent and chromosome is present in the cytosol.
\nTheir DNA (deoxyribonucleic acid) is naked that means nucleosomes are absent. They are haploid and their chromosome is unpaired. They contains single molecule of circular DNA. Hence, this option is incorrect.
\nb) They contain single-strand DNA:<\/strong>
\nIn prokaryotes genome is made by the plasmid and chromosome. They contain only one chromosome.
\nThey contain circular chromosome and introns are absent. In prokaryotes nucleus is absent and chromosome is present in the cytosol.
\nTheir DNA is naked that means nucleosomes are absent. They are haploid and their chromosome is unpaired. They contains single molecule of circular DNA. Hence, this option is incorrect.
\nc) They are located in the cytosol:<\/strong>
\nIn prokaryotes genome is made by the plasmid and chromosome. They contain only one chromosome.
\nThey contain circular chromosome and introns are absent. In prokaryotes nucleus is absent and chromosome is present in the cytosol.
\nTheir DNA is naked that means nucleosomes are absent. They are haploid and their chromosome is unpaired. They contains single molecule of circular DNA. Hence, this option is correct.
\nd) They are associated in linear pairs:<\/strong>
\nIn prokaryotes genome is made by the plasmid and chromosome. They contain only one chromosome.
\nThey contain circular chromosome and introns are absent. In prokaryotes nucleus is absent and chromosome is present in the cytosol.
\nTheir DNA is naked that means nucleosomes are absent. They are haploid and their chromosome is unpaired. They contains single molecule of circular DNA. Hence, this option is incorrect.
\nHence, the correct option is (c) they are located in the cytosol which is the location prokaryotic chromosomes are present.<\/p>\nMicrobiology with Diseases by Taxonomy Chapter 7 Answers 2SA<\/strong><\/span>
\nEukaryotic messenger RNA differs from prokaryotic mRNA:<\/strong>
\nExplanation<\/strong>
\nIn prokaryotes, the site of transcription and translation of mRNA is cytoplasm. In eukaryotes, transcription occurs in the nucleus and translation of mRNA occurs in the cytoplasm. In addition, prokaryotic mRNA is not modified in transcription, whereas in eukaryotes mRNA is modified in transcription by RNA splicing. Eukaryotic mRNA has only one site for initiation and termination of the protein synthesis, whereas in eukaryotes mRNA is monocistronic.
\nFurthermore, in eukaryotes mRNA is synthesized from DNA (deoxyribonucleic acid) template. Therefore, in prokaryotes mRNA is being transcribed from the DNA molecule.
\nProkaryotic mRNA lifespan is very short, whereas eukaryotic mRNA has longer life span and they are metabolically stable. In eukaryotes transcribed mRNA involves major post transcriptional modifications, whereas prokaryotes undergoes little post transcriptional modifications
\nThus, these are the main differences between prokaryotic mRNA and eukaryotic mRNA.<\/p>\nMicrobiology with Diseases by Taxonomy Chapter 7 Answers 3CT<\/strong><\/span>
\nDrugs ddC and AZT are used in AIDS treatment:<\/strong>
\nExplanation<\/strong>
\nDeoxyribonucleic acid (DNA) encodes genetic instructions in all living organisms. It is a nucleic acid, composed of major macro molecules. Moreover, it contains double-stranded helices and organized into long structures known as chromosomes. Additionally, it is used in genetic engineering, forensics, bioinformatics, and DNA nanotechnology.
\nSimilarly, the drugs ddC (dideoxycytidine) and ATZ (azidothymidine) are mainly used in the treatment of the AIDS (acquired immunodeficiency syndrome). Besides, ATZ is a nucleoside analog, reverse transcriptase inhibitor. It is an antiretroviral drug<\/strong> used for treatment of AIDS.
\nTherefore, the drugs ddC and ATZ are nucleotide analog bases, in DNA. These drugs are incorporated in the strand of DNA; they bring to an end in the replication of new DNA strand.<\/p>\nMicrobiology with Diseases by Taxonomy Chapter 7 Answers 3FB<\/strong><\/span>
\nThree effects of point mutations are silence, missense, <\/strong>and non-sense<\/strong>.
\nPoint mutations replace the single base nucleotide with another nucleotide of the genetic material DNA (deoxyribonucleic acid) or RNA (ribonucleic acid). It occurs at the single point during DNA replication.
\nThey are arising from the spontaneous mutations. The rate of mutations is increased by mutagens like UV rays and X-rays. Three effects of point mutations are silence, missence and nonsense mutations.
\nSilence mutations<\/strong> code for the same amino acid, and hence it does not show any effect on the protein functioning. A single nucleotide change in this mutation, but the new codon codes for the same amino acid as wild type.
\nMissense mutations<\/strong> code for entirely different amino acid.
\nNonsense mutations<\/strong> code for a stop codon that terminates the protein synthesis. It converts a functional codon into a termination codon.
\nHence, the correct answers are silence, missense, <\/strong>and non-sense<\/strong>.<\/p>\nMicrobiology with Diseases by Taxonomy Chapter 7 Answers 3MC<\/strong><\/span>
\na) A molecule of RNA (ribonucleic acid ) found in bacterial cells:<\/strong>
\nAn extra chromosomal genetic material is known as plasmid. They are circular deoxyribonucleic acids which are replicate individually of the bacterial chromosome.
\nThey are commonly found as small circular and double stranded DNA (deoxyribonucleic acid) molecules in bacteria. They also present in eukaryotes and archaea.
\nThey are also considering as replicons because they replicate autonomously with in suitable host. They are mainly used as vectors for molecular cloning. Hence, this option is incorrect.
\nb) A distinguished from a chromosome by being circular:<\/strong>
\nAn extra chromosomal genetic material is known as plasmid. They are circular deoxyribonucleic acids which are replicate individually of the bacterial chromosome.
\nThey are commonly found as small circular and double stranded DNA molecules in bacteria. They also present in eukaryotes and archaea.
\nThey are also considering as replicons because they replicate autonomously with in suitable host. They are mainly used as vectors for molecular cloning. Hence, this option is incorrect.
\nc) A structure in bacterial cells formed from plasma membrane:<\/strong>
\nAn extra chromosomal genetic material is known as plasmid. They are circular deoxyribonucleic acids which are replicate individually of the bacterial chromosome.
\nThey are commonly found as small circular and double stranded DNA molecules in bacteria. They also present in eukaryotes and archaea.
\nThey are also considering as replicons because they replicate autonomously with in suitable host. They are mainly used as vectors for molecular cloning. Hence, this option is incorrect.
\nd) Extra chromosomal DNA:<\/strong>
\nAn extra chromosomal genetic material is known as plasmid. They are circular deoxyribonucleic acids which are replicate individually of the bacterial chromosome.
\nThey are commonly found as small circular and double stranded DNA molecules in bacteria. They also present in eukaryotes and archaea.
\nThey are also considering as replicons because they replicate autonomously with in suitable host. They are mainly used as vectors for molecular cloning. Hence, this option is correct.
\nHence, the correct option is (d) extra chromosomal DNA<\/strong> which is known as plasmid.<\/p>\nMicrobiology with Diseases by Taxonomy Chapter 7 Answers 3SA<\/strong><\/span>
\nContrast and comparison of introns and exons:<\/strong>
\nExplanation<\/strong>
\nIntrons are the nucleotide sequence and exons are the nucleic acid sequence, which are related to genes. Moreover, introns are placed between the exons, whereas exons contain code for the complete protein.
\nAdditionally, introns are non-coding sequence and do not carry genetic information and they don\u2019t involve with the coding of proteins, whereas exons are coding DNA sequence and code for proteins.
\nFurthermore, introns are spliced out by the RNA (ribonucleic acid) splicing mechanism after transcription, whereas exons join them. Introns do not contain any open reading frame (ORF). They have only stop codons and random sequences.
\nThus, exons are named as DNA (deoxyribonucleic acid) bases that are translated into mRNA. Introns are present in the genome of the higher vertebrates.<\/p>\nMicrobiology with Diseases by Taxonomy Chapter 7 Answers 4CT<\/strong><\/span>
\nInsertion of three nucleotides is less likely result in deleterious effect than an insertion of single nucleotide:
\nExplanation
\nNucleotides are organic molecules. They are building blocks of the nucleotides (DNA and RNA). They carry energy within the cell and also involve in cell signaling. They are composed of nucleobase, a five carbon sugar, and one or more phosphate groups. They play important role in the metabolism.
\nAdditionally, insertion of three nucleotides gives complete codon to a sequence. It results in incorporation of an amino acid into polypeptide product. Polypeptides have regions, which are flexible for extra amino acid without force.
\nFurthermore, insertion of a single nucleotide into gene sequence produces a shift of the entire reading frame. It results in the changes in the all codons of the downstream insertion.
\nThus, the gene product has an entirely unusual amino acids sequence downstream of the insertion and is non-functional.<\/p>\nMicrobiology with Diseases by Taxonomy Chapter 7 Answers 4FB<\/strong><\/span>
\nInsertion and deletions in the genetic code are also called frame shift<\/strong> mutations.
\nPoint mutations replace the single base nucleotide with another nucleotide of the genetic material DNA (deoxyribonucleic acid) or RNA (ribonucleic acid). It occurs at the single point during DNA replication. It includes insertion, deletions and substitutions.
\nThey are arising from the spontaneous mutations. The rate of mutations is increased by mutagens like UV rays and X-rays.
\nInsertion and deletion of a base pair is called frame shift mutations. In this mutation nucleotide triplets are displaced and creates new sequence of codons, it results in altered polypeptide sequences that mainly affect proteins.
\nA frameshift mutation is caused by deletion or insertion of a nucleotide in a codon. Due to the triplet nature of a reading frame, any insertion or deletion results in a complete different translation. This affects the protein being synthesized.
\nHence, the correct answer is frame shift mutation<\/strong>.<\/p>\nMicrobiology with Diseases by Taxonomy Chapter 7 Answers 4MC<\/strong><\/span>
\na) Chromatin:<\/strong>
\nit is combination of DNA (deoxyribonucleic acid) and protein which makes the content of the nucleus of the cell. Their main functions are packaging DNA in to a small volume to fit in the cell, to strength the DNA to allow mitosis and DNA damage prevention. It also controls gene expression and DNA replication. Hence, this option is incorrect.
\nb) Bacteriocin:<\/strong>
\na proteinaceous toxin produced from the bacteria is known as bacteriocin. It inhibits the growth of similar bacterial strains. It is narrow spectrum antibiotic. Hence, this option is incorrect.
\nc) Histone:<\/strong>
\nHistones are many small, basic proteins most commonly found in association with the DNA in the chromatin of eukaryotes.
\nThey are chief protein component of chromatin. They play very important role in the gene regulation.
\nThey undergo post transcriptional modifications which alter their interaction with DNA and nuclear proteins.
\nThey are basic proteins and their positive charge forms ionic bonds with eukaryotic DNA and stabilizes it. Hence, this option is correct.
\nd) Nucleosome:<\/strong>
\nit is a basic unit of DNA packaging in eukaryotic cells. They form fundamental repeating units of eukaryotic chromatin. Hence, this option is incorrect.
\nHence, the correct option is (c) histone<\/strong> which is basic protein and their positive charge forms ionic bonds with eukaryotic DNA and stabilizes it.<\/p>\nMicrobiology with Diseases by Taxonomy Chapter 7 Answers 4SA<\/strong><\/span>
\nRegulation synthesizes to conserve energy in cells:<\/strong>
\nExplanation<\/strong>
\nPolypeptide synthesis is also known as protein synthesis. Biological cells synthesis new proteins, known as polypeptide synthesis. Moreover, it balances by loss of cellular proteins through degradation, assembly of the proteins by ribosomes. It involves in two steps; transcription and translation and differs in prokaryotes and eukaryotes. For example, photosynthesis is best example for polypeptide synthesis. In photosynthesis, the light energy is converted into chemical energy and depends on the light, carbon dioxide, and temperature.<\/p>\nMicrobiology with Diseases by Taxonomy Chapter 7 Answers 5CT<\/strong><\/span>
\nThe lac operon is an operon, which requires transport and metabolism of the lactose in Escherichia coli<\/strong> and some enteric bacteria<\/strong>. Moreover, it contains lacZ, lacY, and lacA structural genes. These genes are instructed by the enzymes, \u03b2-galactosidase<\/strong>, lactose permease<\/strong>, and thiogalactoside transacetylase<\/strong>.
\nSimilarly, E. coli withstands mutation in the gene for lac operon repressor. The mutation in lac operon prevents repressor binding to the promoter, which results in the continuous transcription of the lac operon genes.
\nAdditionally, the continuous production of enzymes is bacterium is catabolized to lactose. However, continuous production of wild type is disadvantage to cells the lac enzymes is. This is because in continuous production of enzyme if no lactose is available, it leads to the waste cellular resources.<\/p>\nMicrobiology with Diseases by Taxonomy Chapter 7 Answers 5FB<\/strong><\/span>
\nAn operon consists of promoter, operator<\/strong> and series of genes<\/strong> and is associated with a regulatory gene.
\nFunctioning unit of genomic DNA (deoxyribonucleic acid) is known as operon. It consists of promoter, operator and series of genes. It controls the cluster of genes under the promoter.
\nPromoter<\/strong> is a specific nucleotide sequence on DNA (deoxyribonucleic acid) that initiates and allows gene transcription. It is located on the same DNA strand that will be transcribed and is situated upstream of the sequence towards the 3\u2019 region. The promoter sequence will be recognized by RNA (ribonucleic acid) polymerases and by transcription factors. These sequences are usually 100 to 1000 base pairs in length.
\nOperator<\/strong> is a segment of the DNA, which is regulator binding. It is defined as a segment between promoter and the series of genes. It is the site where transcription factors bind. The main function of the operator is to regulate the expression of the gene. The function of the operator is explained very clearly in lac operon.
\nSeries of genes<\/strong> are co-regulated by the operon. These genes code for the enzymes that are necessary for metabolic pathway. For instance, the series of genes present in lac operon are lacZ, lacY, and lacA. They code for different proteins and enzymes that are required in lactose metabolism.
\nHence, the correct answers are promoter, operator, and series of genes<\/strong>.<\/p>\nMicrobiology with Diseases by Taxonomy Chapter 7 Answers 5MC<\/strong><\/span>
\nNucleotides are organic molecules which forms basic building blocks of the nucleic acids like DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).
\na) Carry energy:<\/strong>
\nIn DNA replication process two identical copies are produced from the original DNA molecule. DNA replication is semi conservative model because each strand of the DNA serves as template for the production of complementary strand.
\nIn this process DNA polymerase produce new DNA strand by adding complimentary nucleotides to the template strand. The nucleotide is carry energy in this process.
\nNucleotides are found in four forms, each with a deoxyribose sugar, a phosphate and a base. They are present in the cytosol of the cells as triphosphate nucleotides. Hence, this option is correct.
\nb) Are found in four forms, each with a deoxyribose sugar, a phosphate and a base:<\/strong>
\nIn DNA replication process two identical copies are produced from the original DNA molecule. DNA replication is semi conservative model because each strand of the DNA serves as template for the production of complementary strand.
\nIn this process DNA polymerase produce new DNA strand by adding complimentary nucleotides to the template strand. The nucleotide is carry energy in this process.
\nNucleotides are found in four forms, each with a deoxyribose sugar, a phosphate and a base. They are present in the cytosol of the cells as triphosphate nucleotides. Hence, this option is correct.
\nc) Are present in the cytosol of the cells as triphosphate nucleotides:<\/strong>
\nIn DNA replication process two identical copies are produced from the original DNA molecule. DNA replication is semi conservative model because each strand of the DNA serves as template for the production of complementary strand.
\nIn this process DNA polymerase produce new DNA strand by adding complimentary nucleotides to the template strand. The nucleotide is carry energy in this process.
\nNucleotides are found in four forms, each with a deoxyribose sugar, a phosphate and a base. They are present in the cytosol of the cells as triphosphate nucleotides. Hence, this option is correct.
\nd) All of the above:<\/strong>
\nIn DNA replication process two identical copies are produced from the original DNA molecule. DNA replication is semi conservative model because each strand of the DNA serves as template for the production of complementary strand.
\nIn this process DNA polymerase produce new DNA strand by adding complimentary nucleotides to the template strand. The nucleotide is carry energy in this process.
\nNucleotides are found in four forms, each with a deoxyribose sugar, a phosphate and a base. They are present in the cytosol of the cells as triphosphate nucleotides. Hence, this option is correct.
\nHence, the correct option is (d) all of the above<\/strong> which is nucleotides are used in the replication of DNA for caring energy. They are found in four forms, each with a deoxyribose sugar, a phosphate and a base and they are present in the cytosol of the cells as triphosphate nucleotides.<\/p>\nMicrobiology with Diseases by Taxonomy Chapter 7 Answers 5SA<\/strong><\/span>
\nOperon model in gene regulation:<\/strong>
\nExplanation<\/strong>
\nOperon is functioning unit of the genomic DNA. It is related to regulons, stimulons and modulons. It exists in both prokaryotes and eukaryotes. They are also found in viruses like bacteriophages. Moreover, it was discovered by Jacob and Jacques Monod. Operon has three parts operator, promoter, and repressor.
\nIn addition, during stress circumstances the repressor is bound to the RNA (ribonucleic acid) promoter. Moreover, it increases the RNA polymerase to bind the operator and structural genes of enzymes, which are important for breakdown of the sugars. Thus, in this way operon regulates the gene expression.<\/p>\nMicrobiology with Diseases by Taxonomy Chapter 7 Answers 6CT<\/strong><\/span>
\nNucleotide analogs can be carcinogenic:<\/strong>
\nExplanation<\/strong>
\nNucleotide analogs resemble nucleotide like sequences of DNA (deoxyribonucleic acid). They are mainly used in the treatment of cancer by inhibiting the enzyme reverse transcriptase. Moreover, they are used as antiviral drug; for instance, nucleotides analogs are AZT (azidothymidine) and ddI.
\nAdditionally, nucleotide analogs are carcinogenic; they are incorporated into DNA molecule and cause base pair mismatches, which will synthesis mutations in the new DNA strand sequences.
\nTherefore, they block the DNA replication by preventing further elongation of strand that contains them. It results in inability to replicate and prevent the continued growth of cancer.<\/p>\nMicrobiology with Diseases by Taxonomy Chapter 7 Answers 6FB<\/strong><\/span>
\nIn general, inducible<\/strong> operons are inactive until the substrate of their genes polypeptides is present.
\nOperons can be repressible or inducible. Repressible operon<\/strong> is the operon that is active unless a repressor molecule inhibits it. Inducible operon<\/strong> is the operon that is switched off, but is induced by a small molecule.
\nIn inducible operon, regulatory repressor protein is bound to the operator that ceases the transcription. It is switched off when inducer (chemical) is present.
\nIf inducer molecule is present it binds to the repressor, so repressor does not bind to the operator. It leads to the expression of the operon. Lac operon is example of inducible operon.
\nHence, the correct answer is inducible<\/strong> operon.<\/p>\nMicrobiology with Diseases by Taxonomy Chapter 7 Answers 6MC<\/strong><\/span>
\nDNA polymerase III is functions as a proofreader for newly replicated strand of DNA (deoxyribonucleic acid) .
\na) DNA polymerase III:<\/strong>
\nDNA polymerase III is a holoenzyme and it is involved in the prokaryotic replication. It contains two DNA polymerase embedded in a particle with nine other subunits.
\nThe main function of DNA polymerase III is proofreader for newly replicated strand of DNA. Hence, this option is correct.
\nb) Primase:<\/strong>
\nIt is an enzyme involved in DNA replication. It plays very important role in the DNA replication. It produces short RNA (ribonucleic acid) or DNA segment in some organisms is known as primer. In bacteria it binds to the DNA helicase and forms primosome. Hence, this option is incorrect.
\nc) Helicase:<\/strong>
\nIt is a class of enzyme which is important to all living organisms. They play important function is to unpackaged the genes of organisms. Hence, this option is incorrect.
\nd) Ligase:<\/strong>
\nit is an enzyme which catalyzes the joining of two large molecules by forming a chemical bond. Hence, this option is incorrect.
\nHence, the correct option is (a) DNA polymerase<\/strong> which functions as a proof reader for newly replicated strand of DNA.<\/p>\nMicrobiology with Diseases by Taxonomy Chapter 7 Answers 6SA<\/strong><\/span>
\nComponents and structure of DNA and RNA in prokaryotes:<\/strong>
\nExplanation<\/strong>
\nProkaryotic<\/strong> cells lack nucleus and do not having organelles. The DNA (deoxyribonucleic acid) contains only one chromosome. Moreover, the cells lack membrane bound nucleus and most of them are unicellular organisms. In prokaryotes DNA is located in the nucleoid and is spread throughout the entire cell.
\nAdditionally, the transfer of DNA in prokaryotes is through transduction, conjugation, and transformation. Prokaryotic chromosomes have circular shape and have few proteins. They contain small circular DNA that replicate independently, known as plasmids.
\nFurthermore, prokaryotes contain large RNA (protein). RNA (mRNA) is immediately translated by ribosomes in to proteins. Larger subunit of the ribosomal RNA has 50 Svedberg units (50S) in molecular size and smaller subunit has 30 S in molecular size. These subunits join together to form protein factory. Thus, these are the main difference between prokaryotic DNA and RNA.<\/p>\nMicrobiology with Diseases by Taxonomy Chapter 7 Answers 7CT<\/strong><\/span>
\nDNA polymerase:<\/strong>
\nExplanation<\/strong>
\nDNA polymerase is a cellular polymerase enzyme. They produce DNA (deoxyribonucleic acid) molecules from the nucleotide building blocks. Moreover, plays an important role in the DNA replication, repair, genetic recombination, and reverse transcriptase. It is mainly used in molecular biology, DNA sequencing, and molecular cloning. Besides, it reads DNA strand in replication process and create another strand. It also helps in the production and catalyzes the bonds between nucleic acids in DNA.
\nThus, DNA refers to deoxyribonucleic acid. It denotes the genetic makeup and -ase refers to enzyme or protein. Hence, DNA is named as DNA polymerase.<\/p>\nMicrobiology with Diseases by Taxonomy Chapter 7 Answers 7FB<\/strong><\/span>
\nA daughter DNA molecule is composed of one original strand and one new strand because DNA replication is semi conservative.<\/strong>
\nIn DNA replication two strands of complementary DNA separates in to two original strands.
\nEach strand uses as a template for the synthesis of new complementary strand, so the DNA replication is semi conservative. It contains half original strand and half new strand.
\nSemi conservative replication was confirmed by the Meselson-Stahl experiment.
\nHence, the correct answer is semi conservative<\/strong>.<\/p>\nMicrobiology with Diseases by Taxonomy Chapter 7 Answers 7MC<\/strong><\/span>
\nThe methyl group addition to cytosine of DNA (deoxyribonucleic acid) is known as methylation.
\na) Methylation:<\/strong>
\nAddition of the methyl group to cytosine of deoxyribonucleic acid is known as methylation. It modifies the expression of gene in the cells.
\nIt removed in the zygote formation and reestablished in the cell divisions. It modifies which regulate gene expression. Moreover, it suppresses harmful stretches of deoxyribonucleic acid and the expression of endogenous retroviral genes<\/strong>. It forms bases of chromatin structure.
\nIt plays very important role in the development of all types of cancer. Hence, this option is correct.
\nb) Restriction:<\/strong>
\nRestriction enzyme is used for the cutting DNA at specific recognition nucleotide sequence. It is also known as restriction endonuclease. They are mainly used for the DNA modification and manipulation. Hence, this option is incorrect.
\nc) Transcription:<\/strong>
\nIt is first step of the gene expression. In this process DNA segment is copied into RNA (ribonucleic acid) polymerase. Hence, this option is incorrect.
\nd) Transversion:<\/strong>
\nThe substation of purines for pyrimidines is known as transversion. It can be caused by the ionizing radiation. Hence, this option is incorrect.
\nHence, the correct option is (a) methylation<\/strong> addition of the methyl group to the cytosine of the deoxyribonucleic acid.<\/p>\nMicrobiology with Diseases by Taxonomy Chapter 7 Answers 7SA<\/strong><\/span>
\nDifference in function of RNA polymerase with DNA polymerase:<\/strong>
\nExplanation<\/strong>
\nDNA (deoxyribonucleic acid) polymerase<\/strong> plays an important role in the replication process, but it is not capable of initiating, whereas RNA (ribonucleic acid) polymerase has the capability of initiation. Thymine base is present in DNA, whereas uracil base is present in RNA. RNA is single stranded, whereas DNA is double stranded. In addition, DNA polymerase requires RNA primer for initiating replication, but RNA polymerase does not require any primer.
\nRNA polymerase<\/strong> does not require helicase enzyme to unwind the DNA strands, whereas DNA require helicase enzyme for replication process. Moreover, RNA polymerase is capable of many functions on comparing with DNA polymerase. DNA polymerase starts function at 3\u2019 end. RNA polymerase functions anywhere of the DNA strand, 3\u2019 end to 5\u2019 end direction.<\/p>\nMicrobiology with Diseases by Taxonomy Chapter 7 Answers 8CT<\/strong><\/span>
\nEffect of Corynebacterium diphtheria on cellular metabolism:<\/strong>
\nExplanation<\/strong>
\nCorynebacterium diphtheriae is gram positive bacteria. They mainly cause disease known as diphtheria. The bacteria produce a toxin called as diphtheria toxin. The toxin supports in the alteration of protein function in the host by inactivating the elongation factor (EF-2). Moreover, it slowly shows immediate toxic effect on the cell, because cell requires the productions of proteins continuously. Thus, there is no long term effect because cell is already dead.
\nHence, Corynebacterium diphtheria secretes a toxin, which inactivates elongation factors of eukaryotic cell.<\/p>\nMicrobiology with Diseases by Taxonomy Chapter 7 Answers 8FB<\/strong><\/span>
\nA gene for antibiotic resistance can move horizontally among bacterial cells by transformation, transduction <\/strong>and bacterial conjugation.<\/strong>
\nInsertion of genetic material into the non-bacterial cells is known as transformation<\/strong>. It was demonstrated by the Frederick Griffith in 1928 in Streptococcus pneumoniae.
\nInjection of foreign DNA (deoxyribonucleic acid) by bacteriophage virus in to the host bacterium is known as transduction<\/strong>.
\nTransfer of genetic material between two bacterial cells through direct contact is known as conjugation<\/strong>.
\nBy the process of transformation, transduction and bacterial conjugation antibiotic resistance can move among bacterial cells.
\nHence, the correct answer is transformation, transduction <\/strong>and bacterial conjugation.<\/strong><\/p>\nMicrobiology with Diseases by Taxonomy Chapter 7 Answers 8MC<\/strong><\/span>
\nIn translation the binding site through which tRNA (transfer ribonucleic acid) molecules leave is known as E site.
\na) A site:<\/strong>
\nTranslation is a process that cellular ribosomes produce proteins and also synthesis polypeptides. It is a part of gene expression.
\nIt complete in four process they are; initiation, elongation, translocation and termination. In this process the binding site through which tRNA (transfer ribonucleic acid) molecules leave is known as E site.
\nA site is accommodates a tRNA delivering an amino acid. Hence, this option is incorrect.
\nb) X site:<\/strong>
\nTranslation is a process that cellular ribosomes produce proteins and also synthesis polypeptides. It is a part of gene expression.
\nIt complete in four process they are; initiation, elongation, translocation and termination. In this process the binding site through which tRNA (transfer ribonucleic acid) molecules leave is known as E site. Hence, this option is incorrect.
\nc) P site:<\/strong>
\nTranslation is a process that cellular ribosomes produce proteins and also synthesis polypeptides. It is a part of gene expression.
\nIt complete in four process they are; initiation, elongation, translocation and termination. In this process the binding site through which tRNA (transfer ribonucleic acid) molecules leave is known as E site.
\nP site is holds a tRNA and the growing polypeptide. Hence, this option is incorrect.
\nd) E site:<\/strong>
\nTranslation is a process that cellular ribosomes produce proteins and also synthesis polypeptides. It is a part of gene expression.
\nIt complete in four process they are; initiation, elongation, translocation and termination. In this process the binding site through which tRNA (transfer ribonucleic acid) molecules leave is known as E site. In this site tRNA is exist. Hence, this option is correct.
\nHence, the correct option is (d) E site<\/strong> which is the binding site of the tRNA molecules.<\/p>\nMicrobiology with Diseases by Taxonomy Chapter 7 Answers 8SA<\/strong><\/span>
\nFunction and formation of mRNA, rRNA, and tRNA in eukaryotes and prokaryotes:<\/strong>
\nExplanation<\/strong>
\nThe mRNA (messenger RNA) is large family of the RNA and it transmits genetic information from DNA (deoxyribonucleic acid) to the ribosome. In eukaryotes, translation occurs in ribosomes. Translation is not directly coupled to the transcription. In eukaryotes mRNA contains only one polypeptide.
\nSimilarly, in prokaryotes mRNA<\/strong> is translated into proteins. The mRNA does not require processing or transported. Transcription immediately begins after the end of transcription. In prokaryotes translation is coupled to the transcription. Besides, eukaryotic and prokaryotic mRNA involves in transcription, transport, and translation. Main function of mRNA is to carry genetic information.
\nAdditionally, rRNA<\/strong> (ribosomal RNA) is RNA, component of the ribosome. It is important in the protein synthesis of living organism. Prokaryotes contain 30S small subunit and 50S large subunit. In eukaryotes 28S, 5.8S, 18S, and 5S subunits of four types of cytoplasmic rRNA and 12S and 16S two types of subunits in mitochondria.
\nFurthermore, tRNA<\/strong> plays important role to translate the code words in mRNA. Each specific tRNA molecule contains three base sequences, which base pair with complimentary mRNA. It is specific to amino acid specific, scans and detects mRNA. Its structure resembles with clover leaf and has several extended loops. Thus, acts as tool in the translation process of mRNA.<\/p>\nMicrobiology with Diseases by Taxonomy Chapter 7 Answers 9CT<\/strong><\/span>
\nUse of siRNA to turn off a cancer-inducing gene:<\/strong>
\nExplanation<\/strong>
\nSmall or short interfering RNA (siRNA) belong to a class of double stranded RNA molecules. It plays important role in the RNA (ribonucleic acid) interference path way and post transcriptional gene silencing. Moreover, they are used as a tool in validating gene function and drug targeting of post genome.
\nIn addition, they are used in the turn off of cancerous cells, to produce specific proteins that make them differ from the normal cells. Scientists use this technique to cease the process, which converts a normal cell to cancerous cell from the beginning<\/strong>.<\/p>\nMicrobiology with Diseases by Taxonomy Chapter 7 Answers 9FB<\/strong><\/span>
\nTransposons<\/strong> are nucleotide sequences containing palindromes and genes for protein that cut DNA (deoxyribonucleic acid) strands.
\nTransposons are DNA segments of 700-40,000 bp in length that can move from one place to another place within the genome.
\nThey were discovered by the American scientist McClintock in 1902-1992. They are also known as jumping genes. The action of the transposons is known as transposition<\/strong>. It occurs between the chromosomes and the plasmids. They transfer transposons from one cell to another cell.