E. coli cells infected with bacteriophages having radioactive phosphorus are grown on medium containing normal phosphorus and sulphur and their daughter cells are centrifuged. What will be detected in the supernatant after centrifugation?

In the Hershey-Chase experiment, bacteriophages infect E. coli cells. The genetic material (DNA) of the bacteriophage enters the bacterial cell, while the protein coat remains outside.

The bacteriophages in the given question are labeled with radioactive phosphorus, meaning their DNA is radioactive. However, their protein coats are not labeled and thus contain normal sulphur.

During centrifugation, the heavier bacterial cells (containing the radioactive phosphorus from the viral DNA) settle at the bottom to form the pellet. The lighter viral protein coats (ghosts) remain suspended in the supernatant.

Since the viral protein coats present in the supernatant were not radioactively labeled, they contain normal sulphur. Therefore, normal sulphur will be detected in the supernatant, while radioactive phosphorus will be detected in the pellet.

Answer: Normal sulphur