lecture 8
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Questions and Answers

What direction can DNA polymerase only synthesize DNA?

  • 5’ to 3’ direction (correct)
  • Randomly
  • In both directions
  • 3’ to 5’ direction

    • Which statement accurately reflects a limitation of DNA polymerase's function?

  • It can add nucleotides to any position in a strand.
  • It can synthesize DNA without a primer.
  • It requires a free 3’ OH group on an existing strand of nucleotides to add nucleotides. (correct)
  • It can replace RNA primers with DNA after replication.

    • What is the main role of the origin recognition complex (ORC) in eukaryotic cells?

  • It binds to the ARS to initiate replication. (correct)
  • It synthesizes new DNA strands.
  • It replaces RNA primers with DNA.
  • It relaxes the tension ahead of the replication fork.

    • Which of the following statements best describes the 'end replication problem'?

    <p>It leads to the incomplete replication of linear chromosomes.</p> Signup and view all the answers

    Which mechanism does telomerase use to maintain telomere length?

    <p>It adds DNA sequences to the ends of chromosomes.</p> Signup and view all the answers

    Why might cancer cells have high levels of telomerase activity?

    <p>It allows them to divide rapidly without aging.</p> Signup and view all the answers

    What is required to initiate the synthesis of new DNA during replication?

    <p>RNA primers</p> Signup and view all the answers

    What role does tension relief play in DNA replication?

    <p>It prevents supercoiling ahead of the replication fork.</p> Signup and view all the answers

    What role does heat play in the Polymerase Chain Reaction (PCR)?

    <p>It separates the two strands of DNA.</p> Signup and view all the answers

    How does the self-correcting ability of DNA polymerase function?

    <p>By replacing incorrect bases with the correct ones after synthesis.</p> Signup and view all the answers

    What effect does AZT have when incorporated into a DNA strand?

    <p>It prevents the addition of further nucleotides.</p> Signup and view all the answers

    Why is AZT less likely to be incorporated into human DNA compared to that of HIV?

    <p>Human DNA polymerase has a lower affinity for AZT.</p> Signup and view all the answers

    Which protein's primary job is to unwind the DNA strands during replication?

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

    What is a significant feature of telomerase in relation to cellular aging?

    <p>It extends the telomeres at chromosome ends.</p> Signup and view all the answers

    Which process is directly inhibited by the presence of AZT in the replication of HIV?

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

    What is the primary role of primase during the DNA replication process?

    <p>To provide a starting point for DNA synthesis.</p> Signup and view all the answers

    Which statement correctly describes the direction of DNA synthesis by DNA polymerase?

    <p>All DNA polymerases synthesize DNA in the 5' to 3' direction.</p> Signup and view all the answers

    What characterizes the synthesis of the lagging strand during DNA replication?

    <p>It consists of Okazaki fragments synthesized away from the replication fork.</p> Signup and view all the answers

    What is the primary function of telomerase in cells?

    <p>It maintains telomeric repeat sequences at the ends of chromosomes.</p> Signup and view all the answers

    How do the origins of replication in bacteria compare to those in mammalian cells?

    <p>Bacteria have a single origin of replication, whereas mammals have multiple origins.</p> Signup and view all the answers

    Which statement about DNA replication accuracy is true?

    <p>Certain proteins help ensure accuracy during DNA replication.</p> Signup and view all the answers

    Which statement accurately describes the synthesis of the leading strand during DNA replication?

    <p>It is synthesized continuously towards the replication fork.</p> Signup and view all the answers

    What is the role of telomerase during DNA replication?

    <p>It adds telomeric repeat sequences to the ends of chromosomes.</p> Signup and view all the answers

    Which statement correctly describes the nature of DNA strand synthesis?

    <p>Strands can only be synthesized in a 5’ to 3’ direction.</p> Signup and view all the answers

    Which process occurs primarily on the lagging strand during DNA replication?

    <p>Synthesis of Okazaki fragments in opposite direction of the fork.</p> Signup and view all the answers

    Which component is essential for the initiation of DNA synthesis?

    <p>RNA primase.</p> Signup and view all the answers

    Which protein's primary function is to separate the two strands of DNA during PCR?

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

    What is the role of AZT when incorporated into a growing strand of DNA?

    <p>It prevents additional bases from being added afterwards</p> Signup and view all the answers

    What contributes to human DNA polymerase's lower incorporation rate of AZT compared to HIV reverse transcriptase?

    <p>Higher fidelity of human DNA polymerase during replication</p> Signup and view all the answers

    Why does AZT have a greater effect on HIV than on human cells?

    <p>Human cells have more robust repair mechanisms</p> Signup and view all the answers

    What function does DNA polymerase serve in relation to its ability to correct errors?

    <p>It incorporates bases that are complementary to the template strand</p> Signup and view all the answers

    Which statement best describes the relationship between AZT and thymidine?

    <p>AZT is a thymidine analog that mimics its structure</p> Signup and view all the answers

    Which characteristic of HIV's reverse transcriptase contributes to AZT's efficacy against it?

    <p>It has a much higher affinity for AZT than for natural thymidine</p> Signup and view all the answers

    What is the primary reason for using heat in the Polymerase Chain Reaction?

    <p>To separate the DNA strands for replication</p> Signup and view all the answers

    What is the role of the origin recognition complex (ORC) in eukaryotic DNA replication?

    <p>ORC recruits proteins to initiate replication.</p> Signup and view all the answers

    Which of the following statements accurately describes DNA polymerase's function?

    <p>DNA polymerase requires existing DNA strands to begin synthesis.</p> Signup and view all the answers

    What must happen to RNA primers after DNA synthesis is initiated?

    <p>RNA primers must be replaced with DNA.</p> Signup and view all the answers

    What is a key consequence of the end replication problem during DNA synthesis?

    <p>It causes a gradual loss of DNA sequences from linear chromosomes.</p> Signup and view all the answers

    Which enzyme relieves tension ahead of the replication fork during DNA replication?

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

    Which of the following accurately describes the action of telomerase?

    <p>Telomerase activity is linked to rapid cell division in cancer cells.</p> Signup and view all the answers

    What is the main function of the proteins that coat single-stranded DNA during replication?

    <p>To protect the single strands from degradation.</p> Signup and view all the answers

    What characteristic of prokaryotic chromosomes assists in the replication process?

    <p>They consist of circular DNA, simplifying replication.</p> Signup and view all the answers

    Study Notes

    DNA Replication Key Concepts

    • All known DNA polymerases synthesize DNA in the 5’ to 3’ direction.
    • Leading strand synthesis occurs continuously heading into the replication fork
    • Lagging strand synthesis occurs in Okazaki fragments heading away from the replication fork
    • DNA polymerase starts at origins of replication, which contain binding sites for proteins that initiate the process.
    • DNA polymerase and various other proteins act in a coordinated manner to synthesize both leading and lagging strands.
    • Telomeric repeat sequences at the ends of chromosomes are maintained by the action of telomerase (a reverse transcriptase) that carries its own template RNA.

    The reaction catalyzed by DNA polymerase

    • DNA is double stranded
    • Strands are antiparallel
    • A-T pairs → 2 hydrogen bonds
    • G-C pairs → 3 hydrogen bonds
    • Replication is semiconservative
    • New strands of DNA synthesized 5' to 3'
      • 5' phosphate group
      • 3' hydroxyl group
    • DNA synthesis requires input of energy

    Which of the following is NOT true of DNA polymerase?

    • DNA polymerase cannot synthesize DNA in the 3’ to 5’ direction

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    DNA Replication Lecture 8 - Chapter 5 PDF

    Description

    This quiz covers essential concepts of DNA replication including the roles of DNA polymerases, leading and lagging strand synthesis, and the importance of telomerase. Test your understanding of how DNA is synthesized in a semiconservative manner and the biochemical mechanisms involved. Challenge yourself with key terms and processes related to this fundamental biological process.

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