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Question
Describe the Hershey-Chase experiment in detail.
Solution
- Hershey and Chase worked on viruses that infect bacteria and are called bacteriophages which are composed of DNA and protein.
- Hershey and Chase grew some viruses on a medium that contained radioactive phosphorus (32P) and some others on the medium that contained radioactive sulphur (35S).
- Viruses grown in presence of radioactive phosphorus contained radioactive DNA but not radioactive protein because DNA contains phosphorus.
- Viruses grown in presence of radioactive sulphur contained radioactive protein but not radioactive DNA, because DNA does not contain sulphur, but proteins contain sulphur.
- Radioactive bacteriophages were allowed to infect E. coli bacteria grown on the medium containing normal ‘P’ and ‘S’.
- As the infection proceeded, the viral coats were removed from the bacteria with the help of a centrifuge.
- Bacteria infected with viruses containing radioactive DNA were radioactive, whereas bacteria infected with viruses containing radioactive proteins were not radioactive.
- This indicates that DNA enters the bacterial cells and not protein.
- Thus, by this experiment, Hershey and Chase proved that DNA is the genetic material.
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