DNA Structure and Replication
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Questions and Answers

What is the result of a mutation that completely inhibits telomerase activity?

  • DNA replication occurs without errors.
  • DNA synthesis becomes faster.
  • Ends of replicated DNA are left single-stranded. (correct)
  • The double helix unwinds more efficiently.

    • Which enzyme is likely affected by a mutation that impairs the opening of the DNA double helix during replication?

  • Helicase (correct)
  • Topoisomerase
  • DNA ligase
  • Primase

    • How do RNA and DNA differ in terms of structure?

  • RNA is double-stranded while DNA is single-stranded.
  • RNA contains deoxyribose sugar while DNA contains ribose.
  • RNA has no sugar-phosphate backbone.
  • RNA contains uracil instead of thymine present in DNA. (correct)

    • What type of bond is formed between complementary nitrogenous bases in a DNA double helix?

    <p>Hydrogen bonds</p> Signup and view all the answers

    In DNA replication, how are Okazaki fragments synthesized?

    <p>They are synthesized in the 5' → 3' direction using the lagging strand as a template.</p> Signup and view all the answers

    Which statement best describes semiconservative DNA replication compared to conservative replication?

    <p>One strand of the original double helix is conserved and the other is newly synthesized.</p> Signup and view all the answers

    What structural feature enables DNA to replicate and pass on hereditary information?

    <p>The complementary pairing of nitrogenous bases</p> Signup and view all the answers

    What is the outcome when the hydroxyl group of one nucleotide links to the phosphate group of another?

    <p>A phosphodiester bond is formed.</p> Signup and view all the answers

    What effect would a mutation disabling enzyme 2 have on Neurospora’s ability to grow?

    <p>It would only grow on medium containing Citrulline.</p> Signup and view all the answers

    Which statement accurately describes the function of mRNA?

    <p>It makes a copy of DNA and functions in the synthesis of proteins.</p> Signup and view all the answers

    How does the genetic code exhibit redundancy?

    <p>More than one codon can specify the addition of the same amino acid.</p> Signup and view all the answers

    What structures are essential in the initiation of transcription in bacteria?

    <p>The binding of sigma to the promoter region.</p> Signup and view all the answers

    What occurs during the termination of transcription in bacteria?

    <p>A hairpin secondary structure forms in the RNA transcript, separating it from RNA polymerase.</p> Signup and view all the answers

    What is the relationship between genotype and phenotype?

    <p>Genotype refers to DNA base sequence, while phenotype refers to physical traits resulting from protein products.</p> Signup and view all the answers

    What is the result of a point mutation that changes the mRNA codon CCC to CCA?

    <p>The organism’s genotype changes, but not its phenotype.</p> Signup and view all the answers

    What determines the sequence of RNA during transcription?

    <p>The sequence of the DNA template strand.</p> Signup and view all the answers

    Which of the following processes in eukaryotic cellular respiration occurs in the mitochondria?

    <p>Citric acid cycle</p> Signup and view all the answers

    During which cellular respiration stage is carbon dioxide released?

    <p>Oxidation of pyruvate to acetyl CoA</p> Signup and view all the answers

    In the Hershey-Chase experiment, which radioactive material indicated the genetic material in DNA?

    <p>Radioactive phosphorus (32P)</p> Signup and view all the answers

    What serves as the electron acceptor in fermentation processes?

    <p>Pyruvate</p> Signup and view all the answers

    Which component is NOT part of a nucleotide structure?

    <p>Amino acid</p> Signup and view all the answers

    What distinguishes ribonucleotides from deoxyribonucleotides?

    <p>The hydroxyl group on the 2' carbon</p> Signup and view all the answers

    Which process in cellular respiration is directly driven by an electrochemical gradient maintained by proton pumps?

    <p>ATP synthesis via oxidative phosphorylation</p> Signup and view all the answers

    What was a significant observation during the Hershey-Chase experiment?

    <p>Radioactive 32P was found in the bacterial cells</p> Signup and view all the answers

    Study Notes

    DNA Structure and Replication

    • Hydrogen bonds form between complementary nitrogenous bases in a DNA double helix.

    • A double-stranded DNA molecule containing 120 purines and 120 pyrimidines could be composed of 120 thymine and 120 adenine molecules.

    • Nucleotides are linked together to form a nucleic acid chain through a phosphodiester bond, formed by a dehydration reaction between the hydroxyl group on the second carbon of one nucleotide and the phosphate group on the fifth carbon of the next nucleotide.

    • The complementary pairing of nitrogenous bases allows DNA to replicate and pass on hereditary information to daughter cells.

    • RNA and DNA share a similar sugar-phosphate backbone formed by phosphodiester linkages.

    • The conservative replication hypothesis can be eliminated by data from the first generation of E. coli in the Meselson-Stahl experiment.

    • Semiconservative DNA replication differs from conservative replication in that the DNA strands are separated, and each strand is copied.

    • If one strand of a DNA molecule has the sequence of bases 5'ATTGCA3', the other complementary strand would have the sequence 5'TGCAAT3'.

    • The enzyme topoisomerase breaks and rejoins DNA to mitigate the tension that develops during DNA replication.

    • Okazaki fragments are synthesized using the lagging strand as a template and are synthesized in the 5' → 3' direction.

    • DNA synthesis is continuous for the leading strand and discontinuous for the lagging strand.

    Consequences of Telomerase Inhibition

    • A mutation that completely inhibits telomerase results in single-stranded ends of replicated DNA.

    Proteins Involved in DNA Replication

    • A mutation affecting the cell's ability to open the double helix during DNA replication likely affects helicase.

    Beadle and Tatum's Experiment

    • Beadle and Tatum's experiment with Neurospora crassa led to the "one gene, one enzyme" hypothesis, focusing on the metabolic pathway of arginine production.

    • A mutation disabling enzyme 2 in the arginine pathway would result in Neurospora that can grow on medium containing Citrulline, but not on Ornithine.

    Transcription and Translation

    • RNA is synthesized during the process of transcription.

    • The central dogma describes the flow of genetic information as DNA → RNA → Proteins.

    • Binding of sigma to the promoter region is central to the initiation of transcription in bacteria.

    • The core promoter in prokaryotes is usually composed of the TATA box and -35 box.

    • Transcription begins at the +1 site of a gene in bacterial cells, while translation begins at the Start codon of mRNA.

    • The RNA sequence transcribed from the DNA template strand 5’ – ACTCGCATCGGCA – 3’ is 5’ | UGCCGAUGCGAGU | 3’.

    • Transcription termination in bacteria occurs when a hairpin secondary structure forms in the RNA transcript, allowing it to separate from the RNA polymerase.

    Post-Transcriptional Modification and mRNA Function

    • Mature mRNA is smaller than the primary mRNA transcribed directly from DNA due to post-transcriptional modification that removes introns, producing a shorter spliced mRNA transcript.

    • The primary function of mRNA molecules is to make a copy of DNA and function in the synthesis of proteins.

    Genotype, Phenotype, and the Genetic Code

    • Genotype refers to the DNA base sequence, while phenotype represents the physical traits resulting from the proteins produced.

    • It is false that the genetic code has only a single codon for each amino acid.

    • A codon is the basic unit of the genetic code, consisting of three bases.

    • A point mutation changing the mRNA codon from CCC to CCA alters genotype but not phenotype.

    • The anticodon on the loop of the tRNA base pairs with a codon of mRNA.

    • The genetic code is considered redundant because more than one codon can specify the addition of the same amino acid.

    Cellular Respiration

    • Glycolysis is the only process in cellular respiration that does not occur within the mitochondria.

    • Glycolysis proceeds normally both in the presence and absence of oxygen in eukaryotic cells.

    • The citric acid cycle occurs in the matrix of mitochondria in eukaryotic cells.

    • Oxygen serves as the final electron acceptor in the electron transport chain of aerobic oxidative phosphorylation.

    • Carbon dioxide (CO2) is released during the oxidation of pyruvate to acetyl CoA and the citric acid cycle stages of cellular respiration.

    • Pyruvate serves as the electron acceptor in fermentation.

    • Oxidative phosphorylation utilizes the electrochemical gradient across the inner mitochondrial membrane, maintained by proton pumps, to drive ATP synthesis.

    • Much of the mass lost during exercise is consumed in respiration and exhaled as carbon dioxide and water.

    • Pyruvate is not a high energy intermediate.

    Nucleotides

    • Nucleotides are composed of a nitrogenous base, a phosphate group, and a sugar.

    • Ribonucleotides have a hydroxyl group bonded to their 2' carbon, while deoxyribonucleotides have an H at the same location.

    Hershey-Chase Experiment

    • The Hershey-Chase experiment used radioactive sulfur (35S) and radioactive phosphorus (32P) to determine whether genes are made of proteins or DNA.

    • The Hershey-Chase experiment did not observe radioactive 32P in the viral capsids at the end of the experiment.

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    Description

    This quiz covers key concepts of DNA structure and replication. Topics include the role of hydrogen bonds, nucleotide linking, and the types of DNA replication models. Test your understanding of basic molecular biology principles related to genetic inheritance.

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