In 1952, Alfred Hershey and Martha Chase published a convincing demonstration that DNA (not protein) was the genetic material. The Hershey–Chase experiment was carried out with a virus, called bacteriophage T2, that infects bacteria. Bacteriophage T2 consists of little more than a DNA core packed inside a protein coat. Thus, the virus is made of the two materials that were, at the time, the leading candidates for the genetic material.
In addition to the experiment described in this tutorial, Hershey and Chase performed similar but longer-term experiments, allowing the progeny (offspring) generation of viruses to reproduce in unlabeled bacteria. The resulting viruses contained almost no 35S and none of the parental viral protein. They did, however, contain about one-third of the original 32P—and thus, presumably, one-third of the original DNA. Because DNA was carried over in the viruses from generation to generation but protein was not, the logical conclusion was that the hereditary information was contained in the DNA.
Textbook Reference: Concept 9.2 DNA Replicates Semiconservatively