Alfred Hershey

Alfred Hershey (1908-1997), American geneticist and winner of the 1969 Nobel Prize in physiology or medicine, which he shared with Italian-born American microbiologist Salvador Edward Luria and German-born American biologist Max Ludwig Henning Delbrück for their discoveries concerning the replication mechanism of viruses and their genetic structure. Using the bacteriophage, a simple virus that infects bacteria, the trio established the field of bacterial genetics and helped lay the foundation for modern molecular biology.

Alfred Day Hershey was born on December 4, 1908, in Owosso, Michigan. He received a B.S. in chemistry in 1930 and a Ph.D. in bacteriology in 1934, both from Michigan State University. In 1934 he joined the Department of Bacteriology of Washington University in St. Louis, Missouri, as a research assistant. He was promoted to instructor in 1936, assistant professor in 1938, and associate professor in 1942. In 1950 Hershey moved to Cold Spring Harbor, New York, to join the Carnegie Institution of Washington's Department of Genetics, which was located there. In 1962 he became director of the Carnegie Institution's renamed Genetic Research Unit at Cold Spring Harbor. He retired from active research in 1972, but continued to be an active part of the Cold Springs Laboratory until his death.

During the 1940s Hershey, Luria, and Delbrück performed many important experiments with bacteriophages. They also organized the Phage Group, a group of bacteriophage researchers from around the world who met annually at Cold Spring Harbor, on Long Island, New York, to compare and discuss the results of their work. In 1946 Hershey and Delbrück independently discovered that when two strains of bacteriophage infect the same bacteria, the two viruses could exchange genetic material to produce offspring with different infective capabilities than either parent. This was the first example of genetic recombination in viruses. Six years later, in 1952, Hershey and American geneticist Martha Chase conducted their famous “blender experiment” in which, using a Waring blender, they separated the protein coating of the bacteriophage from its nucleic acid core. They then showed that only the nucleic acid portion was injected into the bacterial cell, and that nucleic acid alone could cause replication and transmit genetic information. This experiment proved that genes were made of the nucleic acid DNA. One year later, James D. Watson and Francis Crick announced the double-helix structure of DNA and suggested how genetic information was actually transmitted. Hershey's work contributed directly to this discovery, and also to the development of vaccines against polio, measles, and mumps.

In addition to receiving the Nobel Prize, Hershey was elected to the National Academy of Sciences (NAS) in 1958.