Q.Hershey and Chase experiment with bacteriophage showed that

Alfred Hershey and Martha Chase's 1952 experiment with bacteriophage T2 provided the conclusive proof that DNA, not protein, is the genetic material, finally overcoming lingering doubt from biologists who felt protein's greater chemical diversity made it a more plausible carrier of hereditary information. Because nucleic acids are rich in phosphorus (but contain no sulphur) while proteins are rich in sulphur, in the amino acids cysteine and methionine, (but contain no phosphorus), Hershey and Chase separately labelled one batch of T2 phage with radioactive phosphorus-32 (marking DNA) and another batch with radioactive sulphur-35 (marking protein). Each labelled phage batch was allowed to infect unlabelled E. coli; the culture was then agitated in a blender to shear off phage material still attached to the outside of the bacteria, and centrifuged to separate the heavier bacterial pellet from the lighter phage debris in the supernatant. Radioactive phosphorus (32P) was found almost entirely in the bacterial pellet, while radioactive sulphur (35S) stayed in the supernatant and never entered the cells; even the next generation of phage carried only 32P. Because only DNA physically entered the bacterium and directed synthesis of the next phage generation, Hershey and Chase concluded that DNA, and not protein, is the material that carries hereditary information from a virus into the cell it infects.