Question

Hershey and Chase experimented with radioactively labelled phosphorus and sulfur to determine that DNA and not protein is the genetic material. Which of the following was essential to this confirming experiment?

Options

• Sulphur is present in amino acids in the protein coat of bacteria.

• Phosphorus is present in high amounts in DNA.

• Phosphorus is not present in amino acids in the protein coat of bacteria.

• All of the above were critical to demonstrating that DNA is involved in the genetic material.

Answer 1

All of the above were critical to demonstrating that DNA is involved in the genetic material.

Explanation:

This experiment was successful because Hershey and Chase used specific chemical markers to distinguish between DNA and proteins. Since sulfur is found in proteins (within certain amino acids) but not in DNA, labelling the viral protein coat with radioactive sulfur (35S) allowed them to track its location. Conversely, because phosphorus is a major component of the DNA backbone but is absent from the protein coat, labelling with radioactive phosphorus (32P) specifically tracked the genetic material. By showing that only the phosphorus entered the bacteria while the sulfur remained outside, they proved that DNA, and not protein, is the hereditary material injected by viruses to replicate.