Mechanisms of Mutation: Spontaneous Mutation
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Questions and Answers

What is the main cause of spontaneous mutation?

  • Enzymatic removal of distortions in the helix
  • Tautomeric forms of the bases (correct)
  • Errors in the replication of DNA
  • Thermodynamically unfavored base-pairing

    • Which base pairing is allowed in DNA replication?

  • A–C and G–T
  • A–T and G–C (correct)
  • A–G and C–T
  • A–G and T–C

    • What is the frequency of the alternative tautomeric forms of the bases at any one point in time?

  • 1 in 100 –200 molecules
  • 1 in 10 –20 molecules
  • 1 in 104 –105 molecules (correct)
  • 1 in 1000 –5000 molecules

    • Why will the imino form of adenine base-pair with cytosine rather than thymine?

    <p>Tautomeric form of adenine</p> Signup and view all the answers

    What is the observed frequency of mutation compared to the frequency of alternative tautomeric forms?

    <p>Many orders of magnitude lower</p> Signup and view all the answers

    What does the text suggest as the problem with the explanation for spontaneous mutation?

    <p>The observed frequency of mutation is lower than expected</p> Signup and view all the answers

    What is one of the mechanisms for repair of damaged or altered DNA?

    <p>Proofreading mechanism</p> Signup and view all the answers

    Which type of strain may have mutation rates many thousand times higher than normal?

    <p>Mutator strains</p> Signup and view all the answers

    What type of conversion can nitrous acid cause in DNA?

    <p>Oxidative deamination</p> Signup and view all the answers

    Which alkylating agent acts by introducing alkyl groups onto the nucleotides at various positions?

    <p>Ethyl methane sulphonate (EMS)</p> Signup and view all the answers

    What type of mutation can intercalating agents like ethidium bromide cause?

    <p>Frameshift mutation</p> Signup and view all the answers

    Which type of agent acts only against growing cells?

    <p>Base analogues</p> Signup and view all the answers

    What can replace thymine in DNA and lead to base pair formation?

    <p>5-bromouracil</p> Signup and view all the answers

    What can uracil pair with in DNA, leading to a change from a C–G pair to U–A and ultimately T–A?

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

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