Class 12 Biology - Chapter Molecular Basis of Inheritance NCERT Solutions | Give an account of Hershey and Chase exp

Hershey and Chase conducted experiments using viruses called bacteriophage which infects bacteria to prove that DNA is the genetic material.

1. Some bacteriophage virus were grown on a medium which contained radioactive phosphorus (³²P) and some were grown in another medium with radioactive Sulphur (³⁵S).
2. Viruses grown in the presence of radioactive phosphorus (³²P) contained radioactive DNA.
3. Similar viruses were been grown in the presence of radioactive Sulphur (³⁵S) that also contained this radioactive protein.
4. Both the radioactive virus types were allowed to infect E.coli separately.
5. Soon after the infection, the bacterial cells were gently agitated in blender to remove viral coats from the bacteria.
6. The culture was also centrifuged to separate the viral particle from the bacterial cell.

Observation and conclusions:

1. Only radioactive phosphorus (³²P) was found to be associated with the bacterial cell, whereas radioactive Sulphur (³⁵S) was only found in surrounding medium and not in the bacterial cell.
2. This indicates that only DNA and not protein coat entered the bacterial cell.
3. This proves that DNA is the genetic material which is passed from virus to bacteria and not protein.

If both DNA and proteins contained Phosphorus and Sulphur, the result might change.