Question

Give an account of Hershey and Chase experiment. What did it conclusively prove? If both DNA and proteins contained phosphorus and sulphur do you think the result would have been the same?

Answer 1

Hershey and Chase Experiment:

• Viruses were grown on two media. One medium contained radioactive phosphorus, and another contained radioactive sulphur.
• Viruses grown on radioactive phosphorus contained radioactive DNA but no such protein because protein does not contain phosphorus.
• Viruses grown on radioactive sulphur contained radioactive protein but no such DNA because DNA does not contain sulphur.
• Radioactive phages were allowed to attach to E.coli bacteria. Once the Infection proceeded, the viral coat was removed from bacteria and then viral particles were separated from bacteria for further analysis.

Observation:

• Radioactive DNA was seen in only those bacteria which were infected with phages grown on radioactive phosphorus.
• Radioactive DNA was not seen in those bacteria which were infected with phages grown on radioactive sulphur.

Conclusion: DNA was found to be the genetic material.

If both the DNA and proteins contained sulphur and phosphorus, it would not have been possible to pinpoint the exact genetic material, i.e. DNA or proteins.