According to the Hershey-Chase experiments, which molecule carries genetic information in bacteriophages?

• A. Protein
• B. DNA
• C. Lipids
• D. Carbohydrates

Answer: (B)

Genetic information must be in a molecule that can store, copy, and transmit instructions to make new viruses. In the Hershey-Chase experiments, they distinguished DNA from protein by labeling each with a different radioactive tag. DNA was labeled with phosphorus, while protein was labeled with sulfur. After allowing infection and then separating the viral coats from the bacterial cells, only the phosphorus label ended up inside the bacteria, where it directed the production of new phages. The sulfur-labeled protein remained outside in the empty coats, not in the cells. This shows that the information needed to build new phages is carried by DNA, not by protein. Lipids and carbohydrates aren’t the carriers of genetic information in this context, and proteins didn’t enter the cells to drive replication.