Hershey, Alfred Day (1908-1997), an American biologist, shared the 1969 Nobel Prize for physiology or medicine with Max Delbruck and Salvador Luria for their work on bacteriophages (viruses that attack bacteria).
In 1945, in separate experiments, Hershey and Luria discovered that both the bacteriophage and the bacterium undergo spontaneous mutation after the infection of the host cell (see Virus ). The virus becomes indistinguishable for a time, while the chemistry and metabolism of the infected host undergo changes. In 1946, Hershey observed in a further experiment that genetic recombination took place in the viruses reproduced within the host cell, rather than just a single gene being replicated. This meant that these organisms could be used by scientists to examine the mechanisms of genetic inheritance, which would be far more difficult in more complicated animal cells.
In 1952, in an experiment using an ordinary kitchen blender, Hershey and his assistant Martha Chase showed that it was only the genetic material of the bacteriophage that was injected into the host on infection and that the protein shell remains attached to the outside of the bacterium. This became known as the blender experiment.
Hershey was born on Dec. 4, 1908, in Owosso, Michigan. In 1934, he received a doctorate from Michigan State College. From 1934 to 1950, he taught and did research at the Department of Bacteriology, Washington University School of Medicine, in St. Louis, Missouri. In 1950, he joined the staff of the Department of Genetics at Carnegie Institution of Washington, where, in 1962, he became the director of the Genetics Research Unit. He died on May 22, 1997.
