Why did Hershey and chase label the viral DNA with radioactive phosphorus and not radioactive sulfur?

Hershey and Chase labeled the viral DNA with radioactive phosphorus because DNA contains phosphorus in its backbone, while proteins contain sulfur in their amino acids. By using radioactive phosphorus, they could specifically track the DNA of the virus and determine whether it was the genetic material responsible for infection. In contrast, labeling with sulfur would have risked confusion, as it would track the viral proteins instead of the DNA. This choice was crucial for demonstrating that DNA, not protein, was the hereditary material in viruses.