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● Hershey and Chase worked on bacteriophages (viruses that infect
bacteria).

● When a bacteriophage infects a bacterium, the viral genetic material
gets attached with the bacterial genetic material and bacteria then

treats the viral genetic material as its own to synthesise more viral
particles.

● Hershey and Chase worked to discover whether it was a protein or
DNA that entered the bacteria from virus.
● They labelled some phages with radioactive sulphur and the others

with radioactive phosphorus.
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● These radioactive phages were used to infect ​ coli​

● E.coli​was then blended and centrifuged to remove viral particles.
● It was observed that bacteria with radioactive DNA were radioactive
while those with radioactive proteins lost their radioactivity.
● This showed that it is the DNA that enters the bacteria from viruses

and not proteins. Hence, it was concluded that DNA is the genetic
material.