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Proteins Required for DNA Synthesis

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  • What is the role of DNA helicase in DNA synthesis?

    DNA helicase unwinds the double-stranded DNA by breaking hydrogen bonds between base pairs, creating the replication fork.

  • What does single-strand binding protein (SSB) do during DNA replication?

    SSB proteins bind to single-stranded DNA to prevent it from re-annealing or forming secondary structures.

  • What is the function of primase in DNA synthesis?

    Primase synthesizes a short RNA primer that provides a starting point for DNA polymerase to begin DNA synthesis.

  • What role does DNA polymerase play in DNA replication?

    DNA polymerase adds nucleotides to the 3' end of the RNA primer, synthesizing the new DNA strand complementary to the template strand.

  • What is the function of DNA ligase in DNA synthesis?

    DNA ligase joins Okazaki fragments on the lagging strand by forming phosphodiester bonds, sealing nicks in the sugar-phosphate backbone.

  • What is the role of sliding clamp protein in DNA replication?

    The sliding clamp holds DNA polymerase firmly onto the DNA template, increasing the enzyme's processivity during synthesis.

  • What does topoisomerase do during DNA replication?

    Topoisomerase relieves the supercoiling tension ahead of the replication fork by cutting and rejoining DNA strands.

  • Why is the RNA primer necessary in DNA synthesis?

    The RNA primer provides a free 3'-OH group for DNA polymerase to start adding DNA nucleotides.

  • Which protein removes RNA primers during DNA replication?

    DNA polymerase I (in prokaryotes) or RNase H (in eukaryotes) removes RNA primers and replaces them with DNA nucleotides.

  • What is the difference between leading and lagging strand synthesis proteins?

    Both strands use similar proteins, but the lagging strand requires repeated primase activity and DNA ligase to join Okazaki fragments.

  • How does DNA polymerase ensure accuracy during DNA synthesis?

    DNA polymerase has proofreading 3' to 5' exonuclease activity to remove incorrectly paired nucleotides.

  • What is the function of the origin recognition complex (ORC) in DNA replication?

    The ORC binds to the origin of replication to initiate the assembly of the replication machinery.

  • What role does replication protein A (RPA) play in eukaryotic DNA synthesis?

    RPA stabilizes single-stranded DNA during replication, similar to SSB in prokaryotes.

  • Which enzyme synthesizes the bulk of DNA on the leading strand in eukaryotes?

    DNA polymerase epsilon synthesizes the leading strand in eukaryotic DNA replication.

  • Which enzyme synthesizes the lagging strand in eukaryotes?

    DNA polymerase delta synthesizes the lagging strand in eukaryotic DNA replication.

  • What is the role of flap endonuclease 1 (FEN1) in DNA replication?

    FEN1 removes RNA primers and flaps during lagging strand synthesis before ligation.

  • How does the clamp loader function in DNA replication?

    The clamp loader loads the sliding clamp onto DNA to enable DNA polymerase processivity.

  • What is the role of telomerase in DNA synthesis?

    Telomerase extends telomeres at chromosome ends to prevent shortening during replication.

  • Why is DNA synthesis semi-conservative?

    Each new DNA molecule contains one original strand and one newly synthesized strand, ensuring genetic continuity.

  • What is the significance of the 5' to 3' directionality in DNA synthesis?

    DNA polymerase can only add nucleotides to the 3' end, so synthesis proceeds in the 5' to 3' direction.