conservative vs semi conservative

    Cards (22)

    • What mechanism do scientists call DNA replication?
      Semi-conservative replication
    • What happens to the DNA double helix during semi-conservative replication?
      It separates into two polynucleotide strands
    • What is produced at the end of semi-conservative replication?
      Two molecules of DNA from one
    • What does each of the two copies of DNA contain after replication?
      One strand from the original and one new strand
    • What was one possibility for how DNA replicated?
      Semi-conservative replication
    • What is the other possibility for DNA replication mentioned?
      Conservative replication
    • What element do all bases in DNA contain?
      Nitrogen
    • What are the two main forms of nitrogen isotopes?
      Nitrogen 14 and nitrogen 15
    • Which nitrogen isotope is more common?
      Nitrogen 14
    • How do nitrogen 15 atoms compare to nitrogen 14 atoms?
      Nitrogen 15 atoms are slightly heavier
    • What did scientists do with the bacteria to study DNA replication?
      They extracted the DNA and centrifuged it
    • What does the position of the DNA band in the centrifuge indicate?
      It depends on how heavy the DNA is
    • Where did DNA containing light nitrogen form a bond in the centrifuge?
      Near the top of the tube
    • Where did DNA containing heavy nitrogen form a bond?
      Near the bottom of the tube
    • What happened when bacteria grown on nitrogen 15 were transferred to nitrogen 14?
      They produced DNA with one strand of each nitrogen
    • What does the intermediate bond pattern indicate after one round of replication?
      DNA contains one strand of nitrogen 14 and one of nitrogen 15
    • What happens after the bacteria replicate one more time on nitrogen 14?
      Another bond appears near the top of the tube
    • How can the results differ if DNA replicates conservatively instead of semi-conservatively?
      There would be no DNA with both nitrogen isotopes
    • What would happen after one round of conservative replication?
      One DNA molecule with nitrogen 15 and one with nitrogen 14
    • What would happen after two rounds of conservative replication?
      One DNA molecule with nitrogen 15 and three with nitrogen 14
    • What are the key steps in the experiment to determine DNA replication type?
      1. Grow bacteria in nitrogen 14.
      2. Extract DNA and centrifuge.
      3. Grow bacteria in nitrogen 15.
      4. Extract DNA and centrifuge.
      5. Transfer to nitrogen 14 and replicate once.
      6. Extract DNA and centrifuge.
      7. Analyze bond patterns.
    • What are the implications of the bond patterns observed in the experiment?
      • Indicates semi-conservative replication.
      • Shows presence of both nitrogen isotopes.
      • Confirms original and new strand combination.
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