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DNA Synthesis and Replication

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Termini in questo insieme (20)

  • What was the key finding of the Griffith experiment?
    Bacteria can transform by taking up external DNA, resulting in genotypic and phenotypic changes.
  • What did the Hershey-Chase experiment demonstrate?
    DNA, not protein, is the genetic material that enters bacteria during bacteriophage infection.
  • What is a bacteriophage?
    A virus that infects bacteria, consisting of a protein coat surrounding nucleic acid.
  • State Chargaff's rules regarding DNA base composition.
    In DNA, %A ≈ %T and %G ≈ %C within a species, but base composition varies between species.
  • What did Rosalind Franklin contribute to DNA research?
    She used X-ray diffraction to capture Photo 51, revealing DNA's helical structure.
  • Describe the structure of DNA as discovered by Watson and Crick.
    DNA is a double helix with two anti-parallel strands and complementary base pairing (A–T, C–G).
  • What is the significance of DNA strands being anti-parallel?
    It allows complementary base pairing and directional synthesis of new strands.
  • What model of DNA replication was confirmed by the Meselson-Stahl experiment?
    The semi-conservative model, where each new DNA molecule has one old and one new strand.
  • What is the origin of replication (ORI)?
    Specific DNA sequences where DNA replication begins.
  • What are replication forks?
    Y-shaped regions where DNA strands separate and replication occurs bidirectionally.
  • What role does topoisomerase play in DNA replication?
    It relieves DNA supercoiling ahead of the replication fork by cutting and rejoining DNA.
  • What is the function of helicase during DNA replication?
    Helicase unwinds the DNA double helix by breaking hydrogen bonds between strands.
  • What do single-strand binding proteins (SSBs) do?
    They bind to and stabilize single-stranded DNA to prevent reannealing and degradation.
  • In which direction do DNA polymerases synthesize new DNA strands?
    DNA polymerases synthesize new strands in the 5' to 3' direction, adding nucleotides to the 3' end.
  • What is the difference between the leading and lagging strands?
    The leading strand is synthesized continuously toward the replication fork; the lagging strand is synthesized discontinuously away from the fork in Okazaki fragments.
  • What enzyme synthesizes RNA primers during DNA replication?
    Primase synthesizes short RNA primers that provide starting points for DNA polymerase.
  • How are Okazaki fragments joined together?
    DNA ligase covalently joins Okazaki fragments to form a continuous strand on the lagging strand.
  • What proofreading ability do DNA polymerases have?
    DNA polymerases have 3' to 5' exonuclease activity that corrects base-pairing errors during replication.
  • What are telomeres?
    Non-coding repetitive DNA sequences at the ends of eukaryotic chromosomes that protect them from degradation.
  • What is the role of telomerase?
    Telomerase extends telomeres in germ and some cancer cells, maintaining chromosome length and cell division capacity.