Question

In the Hershey and Chase experiment, radioactive phosphorus (($^{32}$P)) was used to label:

• A. Protein coat of bacteriophage
• B. RNA of bacteriophage
• C. DNA of bacteriophage
• D. Bacterial cell wall

Hint:

Remember the labels for Hershey-Chase: $^{32}P$ for DNA (phosphate backbone) and $^{35}S$ for protein (sulfur-containing amino acids). This is a crucial distinction.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The question asks about the specific component of a bacteriophage that was labeled with radioactive phosphorus ($^{32}P$) in the Hershey-Chase experiment.

Step 3: Detailed Explanation:
Hershey-Chase Experiment (1952): This landmark experiment provided definitive evidence that DNA, not protein, is the genetic material. They used bacteriophages (viruses that infect bacteria).
Labeling Strategy:
- DNA labeling: DNA contains phosphorus (in its phosphate backbone) but no sulfur. So, they used radioactive phosphorus ($^{32}P$) to specifically label the DNA of the bacteriophage.
- Protein labeling: Proteins contain sulfur (in amino acids like methionine and cysteine) but generally no phosphorus. So, they used radioactive sulfur ($^{35}S$) to specifically label the protein coat of the bacteriophage.
Results: After infection and centrifugation, they found that $^{32}P$ entered the bacterial cells and was passed on to progeny phages, while $^{35}S$ remained outside the cells. This indicated that DNA was the genetic material.
Therefore, radioactive phosphorus ($^{32}P$) was used to label the DNA of the bacteriophage.

Step 4: Final Answer:
Radioactive phosphorus ($^{32}P$) was used to label DNA of bacteriophage.