Question: 146: If DNA contained sulphur instead of phosphorus and proteins contained phosphorus instead of sulfur, what would have been the outcome of Hershey and Chase experiment?
(1) No radioactive sulfur in bacterial cells
(2) Both radioactive sulfur and phosphorus in bacterial cells
(3) Radioactive sulfur in bacterial cells
(4) Radioactive phosphorus in bacterial cells
Answer: Option (3)
Explanation:
In the original Hershey and Chase experiment, DNA was labeled with radioactive phosphorus ^{32}\mathrm{P} because DNA contains phosphorus,
while proteins were labeled with radioactive sulfur ^{35}\mathrm{S} because proteins contain sulfur.
The experiment showed that radioactive phosphorus entered the bacterial cells, proving that DNA is the genetic material.
If DNA had contained sulfur instead of phosphorus, then radioactive sulfur would have been used to label DNA.
During infection, DNA enters the bacterial cell while the protein coat remains outside.
Therefore, radioactive sulfur would have been detected inside the bacterial cells.
Hence, the outcome of the experiment would have been the presence of radioactive sulfur in bacterial cells.