Hershey-Chase experiment successfully proved DNA to be genetic material. The correct sequence of steps followed in this experiment is

Options

A. Blending, Infection, Centrifugation
B. Centrifugation, Infection, Blending
C. Infection, Centrifugation, Blending
D. Infection, Blending, Centrifugation.

Answer

### Step-by-Step Solution:

1. **Understanding the Objective**: The Hershey-Chase experiment aimed to determine whether DNA or protein was the genetic material transferred from the bacteriophage (a virus that infects bacteria) to the bacterial cells.

2. **Preparation of Bacteriophages**: The researchers grew two sets of bacteriophages. One set was labeled with radioactive phosphorus (which labels DNA, as DNA contains phosphorus), and the other set was labeled with radioactive sulfur (which labels proteins, as proteins contain sulfur).

3. **Infection of Bacteria**: The labeled bacteriophages were allowed to infect Escherichia coli (E. coli) bacteria. This step is crucial as it involves the attachment of the bacteriophage to the bacterial cell and the introduction of the viral genetic material into the bacteria.

4. **Blending**: After allowing sufficient time for the bacteriophages to infect the bacteria, the mixture was agitated in a blender. This step was essential to separate the viral protein coats from the bacterial cells, ensuring that only the genetic material (DNA or protein) that entered the bacteria was analyzed.

5. **Centrifugation**: The blended mixture was then subjected to centrifugation. This process separated the heavier bacterial cells from the lighter viral particles. The bacteria, which contained the genetic material, formed a pellet at the bottom of the centrifuge tube, while the remaining viral particles stayed in the supernatant.

6. **Analysis of Radioactivity**: The researchers then analyzed the radioactivity of the bacterial cells. They found that only the bacteria infected with the bacteriophage containing radioactive DNA were radioactive, indicating that DNA was the genetic material that had entered the bacteria. In contrast, bacteria infected with the bacteriophage containing radioactive protein were not radioactive, confirming that proteins did not enter the bacteria.

7. **Conclusion**: The experiment concluded that DNA is the genetic material, as it was the only component that successfully entered the bacterial cells and directed the production of new viral particles.

### Correct Sequence of Steps:
1. Infection
2. Blending
3. Centrifugation