DNA Replication Enzymes and Strands
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Questions and Answers

What role does DNA Topoisomerase play during DNA replication?

  • Synthesizes Okazaki fragments on the lagging strand.
  • Removes RNA primers from synthesized DNA.
  • Relieves additional coiling ahead of the replication fork. (correct)
  • Binds to DNA and moves the replication fork forward.

    • Which statement about DNA Polymerase is true?

  • It assembles nucleotides in both 5’ to 3’ and 3’ to 5’ directions.
  • It works on both leading and lagging strands without distinction.
  • It can initiate synthesis on bare template strands.
  • It requires a primer to begin DNA synthesis. (correct)

    • What distinguishes the leading strand from the lagging strand during DNA replication?

  • The leading strand is synthesized in the same direction as the replication fork, while the lagging strand is not. (correct)
  • The leading strand requires multiple RNA primers, while the lagging strand requires only one.
  • The leading strand is synthesized in fragments, while the lagging strand is continuous.
  • The leading strand can exist without DNA Polymerase, while the lagging strand cannot.

    • In eukaryotes, what is the function of DNA Polymerase γ?

    <p>Replicates mitochondrial DNA.</p> Signup and view all the answers

    Which of the following best describes a degenerate codon?

    <p>A codon that can specify more than one amino acid.</p> Signup and view all the answers

    Study Notes

    DNA Replication Enzymes

    • DNA Helicase: Binds to DNA, moves 5' to 3', separating strands using ATP, and advancing the replication fork.
    • DNA Topoisomerase: Relieves DNA supercoiling ahead of the replication fork.
    • Single-Strand Binding Proteins (SSBs): Maintain the parental DNA strands separated, providing templates.
    • DNA Polymerase: Copies DNA by assembling nucleotides
    • dNTPs: Have three phosphate groups, breaking bonds releases energy to connect nucleotides.
    • Primer Requirement: DNA Polymerase cannot initiate synthesis on bare DNA templates; it needs a primer.
    • 5' to 3' Directionality: DNA polymerase synthesizes in the 5' to 3' direction.
    • Proofreading Capability: Some DNA polymerases can proofread newly added nucleotides.

    DNA Replication Strands

    • Leading Strand: Synthesized continuously in the same direction as the replication fork; requires a single RNA primer.
    • Lagging Strand (Okazaki Fragments): Synthesized discontinuously in fragments (Okazaki fragments) because it is opposite the direction of the replication fork; multiple RNA primers are needed.

    Bacterial DNA Polymerases

    • DNA Polymerase III: Main replication enzyme, crucial for the majority of DNA replication. Multiple subunits.
    • DNA Polymerase I: Removes RNA primers and fills in the gaps with DNA. Single subunit.
    • DNA Polymerases II, IV, and V: Involved in DNA repair, including replication of damaged DNA.

    Eukaryotic DNA Polymerases

    • Diverse Set: Humans possess numerous (12+) DNA polymerases.
    • DNA Polymerase α: Its own built-in primase subunit.
    • DNA Polymerases δ and ε: More efficient synthesis than α.
    • DNA Polymerase γ: Specialized in mitochondrial DNA replication.

    Genetic Code and Translation

    • Codons: Three nucleotides (codon) specify an amino acid; more than one codon can code for the same amino acid.
    • Start and Stop Codons: Specific codons signal the start (AUG) and end (UAA, UAG, UGA) of protein synthesis.
    • Transfer RNA (tRNA): Carries anti-codons to ribosomes, facilitating protein synthesis based on codons.

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    Description

    Explore the essential enzymes and processes involved in DNA replication. This quiz covers DNA helicase, topoisomerase, and the distinctions between leading and lagging strands. Test your knowledge on how these components work together to ensure accurate DNA synthesis.

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