Alfred Day Hershey (1908-1997), US geneticist. Hershey worked at the Carnegie Institution of Washington's Genetics Research Unit at Cold Spring Harbor, New York, USA. In 1952, working with Martha Chase, his studies of bacteriophages proved that DNA (deoxyribonucleic acid) carries genetic information. Their experiment labelled the DNA and protein coats of bacteriophages with different radioactive markers. For this work, Hershey was awarded a share of the 1969 Nobel Prize in Physiology or Medicine. Hershey was Director of the Genetics Research Unit from 1962. Photographed by da Silva, Huntington, New York, in 1969.