Question

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

Answer 1

• Hershey and Chase conducted experiments on bacteriophage to prove that DNA is the genetic material.

1) Bacteriophage viruses were grown on a medium that contained radioactive phosphorus P^32 and some in another medium with radioactive sulfur S^35.
2) Viruses that grow in the presence of radioactive phosphorus contained radioactive DNA.

3) Similarly, viruses grown in presence of radioactive sulfur contained radioactive protein.

4) Both the radioactive virus types were allowed to infect E. coil separately.

5) The infected bacterial cells were agitated in a blender to remove viral coats from the bacteria.

• It was observed that only radioactive phosphorous was found to be within the bacterial cell whereas, radioactive sulfur was only found in the surrounding medium and not in the bacterial cell.
• This proves that only DNA and not protein coat entered the bacterial cell.
• Thus, DNA is the genetic material.
• If both DNA and proteins contained phosphorus and sulfur, the result might change.
• If DNA contained both sulfur and phosphorous then the bacterial cell the would have radioactive sulfur and phosphorous.