Question

Describe the Hershey-Chase experiment in detail.

Answer 1

1. Hershey and Chase worked on viruses that infect bacteria and are called bacteriophages which are composed of DNA and protein.
2. 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).
3. Viruses grown in presence of radioactive phosphorus contained radioactive DNA but not radioactive protein because DNA contains phosphorus.
4. Viruses grown in presence of radioactive sulphur contained radioactive protein but not radioactive DNA, because DNA does not contain sulphur, but proteins contain sulphur.
5. Radioactive bacteriophages were allowed to infect E. coli bacteria grown on the medium containing normal ‘P’ and ‘S’.
6. As the infection proceeded, the viral coats were removed from the bacteria with the help of a centrifuge.
7. Bacteria infected with viruses containing radioactive DNA were radioactive, whereas bacteria infected with viruses containing radioactive proteins were not radioactive.
8. This indicates that DNA enters the bacterial cells and not protein.
9. Thus, by this experiment, Hershey and Chase proved that DNA is the genetic material.