Meselson-Stahl Experiment

1
Meselson-Stahl Experiment

• By Elisa, Andrea, and Allison

2
Meselson-Stahl Experiment
3
Meselson-Stahl Experiment

• Steps in the experiment
• Bacteria was grown in a mediums with heavy
  isotope of nitrogen, 15N.
• The 15N become integrated into the bases, making
  the DNA in the bacteria heavier.
• The bacteria grown with 15N was then moved into a
  medium with 14N.
• Samples of bacteria were periodically taken out.
  
• The DNA in these samples was extracted.

4
Meselson-Stahl Experiment

• There were three types of theories on DNA
  replication semiconservative, conservative, and
  dispersive.
• Meselsons and Stahls experiment proved that DNA
  replication was semiconservative.
• Conservative replication would leave the
  original DNA molecule together, yet create a new
  molecule.
• Dispersive replication would produce two DNA
  molecules with sections of both old and new DNA
  along each strand.
• Semiconservative replication would be made of
  both old and new DNA, with each molecule composed
  of one old strand and one new strand.

5
Meselson-Stahl Experiment

• The DNA with 15N was heavier and denser than the
  DNA with 14N.
• The DNA was dissolved in cesium chloride and spun
  in a centrifuge, and so separated the DNA strands
  by their density
• The cesium ions moved toward the bottom of the
  centrifuge tube, and so was denser at the bottom.
  
• The DNA moved toward the bottom until their
  density was equal to the density of cesium ions.
  

6
Meselson-Stahl Experiment

• Results DNA replicates semiconservatively

7
(No Transcript)
8
Bazinga!