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Meselson-Stahl Experiment quiz #3

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  • How did Meselson and Stahl use nitrogen isotopes to distinguish between old and new DNA strands in their experiment?
    Meselson and Stahl grew bacteria in nitrogen-15 (N15) to label old DNA strands, then switched to nitrogen-14 (N14) for new DNA synthesis, allowing them to track the distribution of old and new strands after replication.
  • Why is the semiconservative model of DNA replication important for understanding genetic inheritance?
    The semiconservative model explains how genetic information is accurately passed from one generation to the next, as each new DNA molecule retains one original strand as a template.
  • What is the main conclusion of the Meselson-Stahl experiment regarding DNA replication?
    The Meselson-Stahl experiment concluded that DNA replication follows the semiconservative model, where each new DNA molecule contains one old (parental) strand and one newly synthesized strand.
  • How did Meselson and Stahl use nitrogen isotopes to distinguish between old and new DNA strands in their experiment?
    They grew bacteria in nitrogen-15 (N15) to label old DNA strands, then switched to nitrogen-14 (N14) for new DNA synthesis, allowing them to track the distribution of old and new strands after replication.
  • What does the semiconservative model of DNA replication state about the composition of new DNA molecules?
    It states that each new DNA molecule consists of one original (parental) strand and one newly synthesized strand.
  • Why is the semiconservative model of DNA replication important for understanding genetic inheritance?
    The semiconservative model explains how genetic information is accurately passed from one generation to the next, as each new DNA molecule retains one original strand as a template.
  • What were the three competing models of DNA replication tested by Meselson and Stahl?
    The three models were the conservative, semiconservative, and dispersive models of DNA replication.
  • Which two models of DNA replication were disproven by the Meselson-Stahl experiment?
    The conservative and dispersive models were disproven by the experiment.
  • In the Meselson-Stahl experiment, what did the use of N15 and N14 isotopes allow scientists to observe?
    The isotopes allowed scientists to distinguish between old (N15-labeled) and new (N14-labeled) DNA strands after replication.
  • What is the key feature of the semiconservative model that differentiates it from the conservative and dispersive models?
    The semiconservative model produces DNA molecules with one old and one new strand, while the conservative model keeps the original molecule intact and the dispersive model mixes old and new DNA within each strand.