Alfred Hershey, the American geneticist, was born December 4, 1908 in Owosso, Michigan. He attended Michigan State University and in 1930 received his B. S. in chemistry and 1934 his Ph. D. in bacteriology. In that same year he was given the position of research assistant at the Department of Bacteriology of Washington University, St. Louis, Missouri. Hershey was promoted to instructor in 1936, assistant professor in 1938 and associate professor in 1942.

Throughout the 1940's Hershey worked with Italian microbiologist Salvador Edward Luria and German physicist Max Ludwig Henning Delbruck performing experiments with bacteriophages, which are viruses that infect bacteria. They organized the "Phage Group", a team of bacteriophage researchers who met every year at Cold Spring Harbor to discuss their work and advances. While Hershey and Delbruck were working together in 1946, they observed that when two different strains of bacteriophages have infected the same bacteria, the two viruses may exchange genetic information. They then produce offspring with different infective natures than either parent had. This was the first example of genetic recombination in viruses.

He moved to Cold Spring Harbor, New York to join the Carnegie Institution of Washington's Department of Genetics in 1950. In 1952, Hershey and American geneticist Martha Chase performed their famous "blender experiment." Using a kitchen blender, they separated the protein coating from the bacteriophage's nucleic acid core. They injected nucleic acid into the bacterial cell and found that the acid itself caused replication and transmission of genetic information, not its protein components. This proved that genes are made of the nucleic acid DNA. One year later James Watson and Francis Crick announced the double-helix structure of DNA and a theory on how genetic material is passed. He then became director of the Carnegie Institution, renamed Genetic Research Unit at Cold Spring Harbor in 1962. Hershey's later research helped the development of vaccines for polio, measles and mumps. Hershey was awarded the 1969 Nobel Prize in physiology or medicine, along with Luria and Delbruck, for their discovery on the replication of viruses and their genetic structure. He retired from active research in 1972 but was a constant figure around the lab until his death in May of 1997.