Meselson and Stahl Experiment: Semiconservative DNA Replication ||Class 12 Biology

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Matthew Meselson and Franklin Stahl in 1958 perform an experiment on Escherichia coli (E. coli).

Outline of the experiment are
     1. E. coli was grown in a medium containing 15NH4Cl as the only nitrogen source for many generations. 15N got incorporated into newly synthesised DNA (and other nitrogen containing compounds). This heavy DNA molecule could be distinguished from the normal DNA by centrifugation in a cesium chloride (CsCl) density gradient.

       2. They then transferred the cells into a medium with normal 14NH4Cl and took samples at various definite intervals as the cells multiplied and extracted the DNA that remained as double- stranded helixes. DNA samples were separated Independently on CsCL gradient to measure DNA densities.

       3. The DNA obtained from the sample of the growth of one generation after the transfer from 15N to 14N medium, had a hybrid or intermediate density.

      4. While the DNA obtained from the sample growth after another generation (second generation), consisted equal amount of hybrid DNA and light DNA.

       5. Taylor and colleagues in 1958 similar experiments on "Vicia faba" (faba beans) found that the results were the same, i.e. DNA replicates semiconservatively.


Location: India

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