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Meselson-Stahl Experiment exam

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  • Meselson-Stahl Experiment
    An experiment that demonstrated DNA replication follows the semiconservative model.
  • Semiconservative Model
    A model of DNA replication where each new DNA molecule consists of one parental strand and one newly synthesized strand.
  • What isotopes were used in the Meselson-Stahl experiment?
    Nitrogen-15 (N15) for old strands and Nitrogen-14 (N14) for new strands.
  • Conservative Model
    A disproven model of DNA replication where the original DNA molecule is conserved and new molecules are entirely new.
  • Dispersive Model
    A disproven model of DNA replication where the original DNA molecule is dispersed throughout the new molecules.
  • What organism did Meselson and Stahl use in their experiment?
    Escherichia coli (E. coli).
  • What does the semiconservative model imply about the parental DNA strands?
    They act as templates for the synthesis of new complementary strands.
  • Nitrogen-15 (N15)
    An isotope used to label old or parental DNA strands in the Meselson-Stahl experiment.
  • Nitrogen-14 (N14)
    An isotope used to label newly synthesized DNA strands in the Meselson-Stahl experiment.
  • What was the main conclusion of the Meselson-Stahl experiment?
    DNA replicates via the semiconservative model.
  • What did the conservative model suggest about DNA replication?
    The original DNA molecule remains conserved, and new molecules are entirely new.
  • What did the dispersive model suggest about DNA replication?
    The original DNA molecule is dispersed throughout the new molecules.
  • What was the key visual indicator in the Meselson-Stahl experiment?
    The use of different nitrogen isotopes (N15 and N14) to distinguish old and new DNA strands.
  • What did Meselson and Stahl switch E. coli to after growing them in N15?
    Media containing Nitrogen-14 (N14).
  • What does the term 'semiconservative' mean in the context of DNA replication?
    Partially conservative; each new DNA molecule has one old strand and one new strand.
  • What was disproven by the Meselson-Stahl experiment?
    The conservative and dispersive models of DNA replication.
  • What color represented N15-labeled DNA strands in the experiment?
    Darker blue.
  • What color represented N14-labeled DNA strands in the experiment?
    Light blue.
  • What is the significance of the Meselson-Stahl experiment in molecular biology?
    It provided foundational understanding of DNA replication, crucial for grasping genetic inheritance.
  • Who were the scientists behind the Meselson-Stahl experiment?
    Matthew Meselson and Franklin Stahl.
  • What year was the Meselson-Stahl experiment conducted?
    1958.
  • What does the semiconservative model ensure during DNA replication?
    Each new DNA molecule is identical to the original, ensuring accurate genetic inheritance.
  • What was the initial growth condition for E. coli in the experiment?
    Grown in Nitrogen-15 (N15) isotope.
  • What happens to the parental DNA strands during semiconservative replication?
    They separate and act as templates for new complementary strands.
  • What did the green check mark indicate in the experiment's results?
    Confirmation that the semiconservative model is the correct model of DNA replication.
  • What did the red X's indicate in the experiment's results?
    Disproval of the conservative and dispersive models of DNA replication.
  • What is the role of complementary base pairing in semiconservative replication?
    Ensures that new DNA strands are accurately synthesized based on the parental template.
  • What is the primary takeaway from the Meselson-Stahl experiment?
    DNA replication is semiconservative, with each new molecule containing one old and one new strand.