Question

Which is incorrect about the Hershey and Chase experiment?

• A. Viruses grown in the presence of radioactive phosphorus contained radioactive protein but not radioactive DNA
• B. Both A and B
• C. Viruses grown on radioactive sulphur contained radioactive DNA but not radioactive protein
• D. None of the above

Answer 1

The correct option is B Both A and B

Part 1: Hershey and Chase experiment
In 1952 Alfred Hershey and Martha Chase conducted an experiment in which they infected Escherichia coli with $T_2$ bacteriophage to prove that the genetic material is DNA and not proteins.

● The $T_2$ bacteriophage is made up of DNA and protein coat. It infects the bacteria and multiplies inside it.
● DNA contains phosphorus and protein contains sulphur.
● One batch of the phage was grown in a medium with radioactive phosphorus ${(}^{32}P)$, and the other was grown in a medium with radioactive sulphur ${(}^{35}S)$.
● The phage DNA was incorporated with radioactive phosphorus and the phage protein was incorporated with radioactive sulphur.
● Then these labelled phages were allowed to infect bacteria grown in a normal medium.
● After the infection, the infected bacteria was broken down by blender and centrifuged.
● The bacterial cells infected with phages having radiolabeled DNA showed the presence of radioactive phosphorus inside the cell.
● In case of the bacterial cells infected with radiolabeled protein coat, radioactive sulphur was present outside the cell.
● This shows DNA is the genetic material not protein.


Final answer
(c) Both A and B