In the Hershey-Chase experiment, which component of the phage was radioactively labeled with 32P?

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

Answer: (C)

This question tests which phage component actually carries genetic information, as shown by tracking what enters the bacterial cell during infection. In the Hershey–Chase experiment, two different labels were used: phosphorus-32 to label DNA and sulfur-35 to label protein. Phosphorus is a key part of the DNA backbone, whereas proteins contain sulfur-rich amino acids but not the DNA backbone. After infection, the radioactivity found inside the bacterial cells came from the 32P label, not from the 35S label, demonstrating that DNA—not protein—was transmitted into the cell and acted as the genetic material. So, the component labeled with 32P is DNA.