Describe the experiment of Hershey and Chase to prove that DNA is the genetic material.

Explanation

(1) Hershey and Chase performed experiments on bacteriophages which are viruses that infect bacteria. Bacteriophages are composed of DNA and protein.
(2) When they infect the bacterial cell, they inject their genetic material into bacteria. For finding out what is the nature of genetic material. Hershey and Chase used radioactive phosphorus `(P^(32))` in the medium for some viruses and for other viruses they used radioactive sulphur `(S^(35))`.
(3) DNA has phosphorus but no sulphur whereas proteins have sulphur but no phosphorus. Thus some viruses were with radioactive DNA (those labelled with `S^(35)`).
(4) Both radioactive labelled viruses were used to infect E.coli bacteria. After some time of infection, the viruses were centrifuged and their viral coats were separated.
(5) Bacteria which were infected with viruses having radioactive DNA also show radioactive characters.
(6) Bacteria which were infected with viruses having radioactive protiens did not show radioactive characters. This shows that DNA enters the bacterial cells at the time of infecting and not the protien.