DNA Structure And Replication Sample Questions

9 Questions | Total Attempts: 156

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Structure Of DNA Quizzes & Trivia

Questions and Answers
  • 1. 
    Which of the following statements regarding a double-helical molecule of DNA is true?
    • A. 

      All hydroxyl groups of pentoses are involved in linkages

    • B. 

      Bases are perpendicular to the axis

    • C. 

      Each strand is identical

    • D. 

      Each strand has parallel, 5’ to 3’ direction

    • E. 

      Each strand replicates itself

  • 2. 
    A sample of human DNA is subjected to increasing temperature until the major fraction exhibits optical density changes due to disruption of its helix (melting or denaturation).  A smaller fraction is atypical in that it requires a much higher temperature for melting.  The smaller, atypical fraction of DNA must contain a higher content of
    • A. 

      Adenine plus cytosine

    • B. 

      Cytosine plus guanine

    • C. 

      Adenine plus thymine

    • D. 

      Cytosine plus thymine

    • E. 

      Adenine plus guanine

  • 3. 
    It is well know that DNA polymerases synthesize DNA only in the 5’ to 3’ direction.  Yet, at the replication fork, both strands of parental DNA are being replicated with the synthesis of new DNA.  How is it possible that while one strand is being synthesized in the 5’ to 3’ direction, the other strand appears to be synthesized in the 3’ to 5’ direction?  This apparent paradox is explained by
    • A. 

      3’ to 5’ DNA repair enzymes

    • B. 

      3’ to 5’ DNA polymerase

    • C. 

      Okazaki fragments

    • D. 

      Replication and immediate crossover of the leading strand

    • E. 

      Lack of RNA primers on one of the strands

  • 4. 
    A child presents with severe growth failure, accelerated aging that causes adult complications such as diabetes and coronary artery disease, and microcephaly (small head) due to increased nerve cell death.  In vitro assay of labeled thymidine incorporation reveals decreased levels of DNA synthesis compared to controls, but normal-sized labeled DNA fragments.  The addition of protein extract from normal cells, gently heated to inactivate DNA polymerase, restores DNA synthesis in the child’s cell extracts to normal.  Which of the enzymes used in DNA replication is likely to be defective in this child?
    • A. 

      DNA-directed DNA polymerase

    • B. 

      Unwinding proteins

    • C. 

      DNA polymerase I

    • D. 

      DNA-directed RNA polymerase

    • E. 

      DNA ligase

  • 5. 
    If a completely radioactive double-stranded DNA molecule undergoes two rounds of replication in a solution free of radioactive label, what is the radioactivity status of the resulting four double-stranded DNA molecules?
    • A. 

      Half should contain no radioactivity

    • B. 

      All should contain radioactivity

    • C. 

      Half should contain radioactivity in both strands

    • D. 

      One should contain radioactivity in both strands

    • E. 

      None should contain radioactivity

  • 6. 
    Which of the following descriptions of DNA replication is not common to the synthesis of both leading and lagging strands?
    • A. 

      RNA primer is synthesized

    • B. 

      DNA polymerase III synthesizes DNA

    • C. 

      Helicase (rep protein) continuously unwinds duplex DNA at the replication fork during synthesis

    • D. 

      Nucleoside monophosphates are added in a 5’ to 3’ direction along the growing DNA chain

    • E. 

      DNA ligase repeatedly joins the ends of DNA along the growing strand

  • 7. 
    Which of the following enzymes can be described as a DNA-dependent RNA polymerase?
    • A. 

      Primase

    • B. 

      DNA ligase

    • C. 

      DNA gyrase

    • D. 

      RNA polymerase III

    • E. 

      Reverse transcriptase

  • 8. 
    Mammalian chromosomes have specialized structures with highly repetitive DNA at their ends (telomeres).  Which aspect of telomeric DNA replication is different from that of other chromosomal regions?
    • A. 

      The DNA polymerase uses an RNA primer but does not degrade it

    • B. 

      The DNA polymerase contains an RNA molecule that serves as template for DNA synthesis

    • C. 

      The DNA polymerase must cross-link the 5’ and 3’ termini

    • D. 

      The DNA polymerase has a  subunit that facilitates binding to repetitive DNA

    • E. 

      The DNA polymerase does not use an RNA template or primer

  • 9. 
    Which of the following statements correctly describes eukaryotic nuclear chromosomal DNA?
    • A. 

      Each discontinuous piece making up the chromosomes of eukaryotes is about the same size as each prokaryotic chromosome

    • B. 

      Unlike bacterial DNA, no histones are associated with it

    • C. 

      It is not replicated semiconservatively

    • D. 

      It is a linear and unbranched molecule

    • E. 

      It is not associated with a specific membranous organelle

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