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Genetics: DNA Structure and Replication

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Terms in this set (21)

  • Which strains of Streptococcus caused disease in Griffin's transformation experiment?
    Living IIS and Living IIR mixed with heat-killed IIS caused disease in mice.
  • What type of ring is found in the nitrogenous base of DNA?
    DNA contains a purine ring in its nitrogenous bases.
  • What chemical groups are labeled (X) and (Y) in DNA's sugar-phosphate backbone?
    (X) is H and (Y) is OH in DNA's 2-deoxyribose sugar.
  • What chemical groups are labeled (X) and (Y) in RNA's sugar-phosphate backbone?
    (X) is OH and (Y) is OH in RNA's ribose sugar.
  • Which of Chargaff's rules is NOT consistent with his findings?
    (A + C) = (G + T) is not consistent with Chargaff's base composition rules.
  • What does the term 'melting temperature' (Tm) mean in genetics?
    Tm is the temperature at which 50% of DNA strands denature or unwind.
  • What are the three models of DNA replication?
    Conservative, semiconservative, and dispersive replication models.
  • Which DNA replication model was supported by the Meselson-Stahl experiment?
    The experiment supported the semiconservative model of DNA replication.
  • What isotope was used in the Meselson-Stahl experiment to label DNA?
    15N (heavy nitrogen isotope) was used to label DNA in E. coli.
  • What is the role of DNA polymerase I in bacterial DNA replication?
    DNA Pol I removes RNA primers and fills in gaps with DNA nucleotides.
  • What is the main function of DNA polymerase III in bacteria?
    DNA Pol III is the primary enzyme for DNA chain elongation during replication.
  • In which direction does DNA polymerase synthesize DNA?
    DNA polymerase synthesizes DNA in the 5' to 3' direction.
  • What is the function of single-stranded binding proteins (SSBPs) during replication?
    SSBPs stabilize single-stranded DNA to prevent the helix from reforming.
  • What enzyme synthesizes the RNA primer during DNA replication?
    Primase, an RNA polymerase, synthesizes the RNA primer.
  • How is the lagging strand synthesized during DNA replication?
    The lagging strand is synthesized discontinuously as Okazaki fragments.
  • What enzyme seals the nicks between Okazaki fragments?
    DNA ligase catalyzes phosphodiester bond formation to join fragments.
  • What is the role of DNA gyrase during replication?
    DNA gyrase relieves supercoiling tension ahead of the replication fork.
  • How do DNA polymerases proofread newly synthesized DNA?
    They use 3' to 5' exonuclease activity to remove incorrect nucleotides.
  • What problem do telomeres solve in eukaryotic chromosomes?
    Telomeres protect chromosome ends from degradation and prevent fusion.
  • What is the 'end-replication problem' in linear chromosomes?
    DNA polymerase cannot fully replicate the 5' ends, causing progressive shortening.
  • Which cells maintain telomerase activity?
    Stem cells and cancer cells maintain telomerase activity to preserve telomere length.