Semi-conservative

    Cards (21)

    • What type of replication 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
    • How many molecules of DNA are produced at the end of semi-conservative replication?
      Two molecules of DNA
    • What does each of the two copies of DNA contain after replication?
      One strand from the original and one new strand
    • In what decade was the structure of DNA first discovered?
      1950s
    • What was one possibility for how DNA replicated when it was first discovered?
      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 depend on?
      How heavy the DNA is
    • Where did the DNA band form when grown on nitrogen 14?
      Near the top of the tube
    • Where did the DNA band form when grown on nitrogen 15?
      Near the bottom of the tube
    • What happened when bacteria grown on nitrogen 15 were transferred to nitrogen 14?
      The DNA produced a band in between the two bands
    • What does the intermediate band indicate about the DNA strands?
      It contains one strand of nitrogen 14 and one of nitrogen 15
    • What happens when the bacteria replicate one more time on nitrogen 14?
      It produces a bond pattern with two bands
    • How would the results differ if DNA replicated conservatively?
      One molecule would contain only nitrogen 15
    • What would be the bonding pattern after two rounds of conservative replication?
      One molecule with nitrogen 15 and three with nitrogen 14
    • What are the key steps in the experiment to determine DNA replication type?
      1. Extract DNA from bacteria.
      2. Centrifuge to observe band position.
      3. Grow bacteria in nitrogen 15.
      4. Transfer to nitrogen 14 and replicate.
      5. Analyze band positions after centrifugation.
    • What are the implications of the semi-conservative replication model?
      • Each new DNA molecule has one original strand.
      • Ensures genetic continuity.
      • Supports the accuracy of DNA replication.