Alfred Hershey and Martha Chase in 1952 worked with viruses that infect bacteria called bacteriophages.

The bacteriophage attaches to the bacteria and its genetic material then enters the bacterial cell. The bacterial cell treats the viral genetic material as if it was its own and subsequently manufactures more virus particles. They worked to discover whether it was protein or DNA from the viruses that entered the bacteria. 

They grew some viruses on a medium that contained radioactive phosphorous and some others on medium that contained radioactive sulphur. Viruses grown in the presence of radioactive phosphorous contained radioactive DNA but not radioactive protein because DNA contains phosphorus but protein does not. Similarly, viruses grown on radioactive sulphur contained radioactive protein but not radioactive DNA because DNA does not contain sulphur. 

Radioactive phages were allowed to infect to E. coli bacteria. Then as the infection proceeded, the viral coats were removed from the bacteria by agitating them in a blender. The virus particles were separated from the bacteria by spinning them in a centrifuge. 

Bacteria which was infected with viruses that had radioactive DNA were radioactive, indicating that DNA was the material that passed from the virus to the bacteria. Bacteria that were infected with viruses that had radioactive proteins were not radioactive. This indicates that proteins didn’t enter the bacteria from the viruses. DNA is therefore the genetic material that is passed from virus to bacteria.