Question
What is ‘semi-conservative’ DNA replication? How was it experimentally proved and by whom?
✓
Answer
After the completion of replication (of the DNA molecule into two)) each DNA molecule will have one parental strand and newly synthesised strand.
Meselson and Stahl
- E.coli grown in medium containing 15NH4CL (15N - heavy Nitrogen) for many generations to ensure that all DNA in the bacteria were heavy,
- Heavy E.coli transferred to a medium with normal 14NH4CL,(after 20 minutes) DNA of generation I extracted to measure their densities, they were of intermediate density,
- After 40 minutes DNA of II generation were extracted and tested for their densities, they were of equal amounts of (hybrid) intermediate DNA, and light DNA/14NH4Cl.
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