Hershey and chase experiment

Experiment with T2 bacteriophages :-

Viruses that infect bacteria and replicate inside it.

• The function of DNA and protein could be found out by labelling them with radioactive tracers DNA contain phosphorus but not sulphur.
• Similarily protein of phage contains sulphur but not phosphorus,

Now some bacteriophages were grown in radioactive phosphorus medium. So that there DNA will be radioactive but protein will not be-radioactive because protein does not contain phosphorus.
Similarly some were grown in the radioactive sulphur medium. So that the protein coat will be radioactive but dna will not be the radioactive one.

Bacteriophage with radioactive DNA attached to bacteria.

Three steps were followed:

Infection: Both types of labelled cells were allowed to infect normally cultured bacteria in separate experiments.

Blending: These bacterial cells were agitated in a blender to break the contact between virus and bacteria.

Centrifugation: The virus particles were separated from the bacteria by spinning them in a centrifuge.

Result
Bacterial cells showed the presence of fradioactivity , no radioactivity detected in supernatant

Bacteriophages with radioactive protein attach to bacteria.

Similarly, bacteria was infected.
Agitated in a blender to separate phage particles from the E.coli bacteria cells.
Centrifugation seperated the phages particles as supernatent.

Result :
Bacteria that were infected with viruses that had radioactive were not radioactive proteins This indicates that proteins did not enter the bacteria from the virus.