(a) Hershey and Chase carried their experiment in three steps : infection, blending, centrifugation. Explain each step.
(b) Write the conclusion and interpretation of the result they obtained.

Explanation

(a) Hershey and Chase worked with viruses that infect bacteria called bacteriophages.
(i) Infection : Radio active phages were allowed to attach E. coli bacteria.
(ii) Blending : Then, as the infection proceeded, the viral coats were removed from the bacteria by agitating them in the blender.
(iii) Bacteria which was infected with viruses that had radioactive DNA were radioactive, indicating that DNA was the material that passed from the virus to the bacteria. Bacteria that were infected with viruses that had radioactive proteins were not radioactive.
This indicates that proteins did not enter the bacteria from the viruses. DNA is, therefore, the genetic material that is passed from virus to bacteria.