born Dec. 14, 1909, Boulder, Colo., U.S.
died Nov. 5, 1975, New York, N.Y., U.S.
He worked with George Wells Beadle at Stanford University, where they confirmed that all biochemical processes in organisms are ultimately controlled by genes, that these processes can be broken down into a series of individual sequential chemical reactions, each controlled by a single gene, and that mutation of a single gene changes the cell's ability to carry out only a single chemical reaction. Each gene was found to determine the structure of a specific enzyme (the "one gene, one enzyme" hypothesis). With Joshua Lederberg , Tatum discovered the occurrence of genetic recombination , or "sex," between certain bacteria. Largely because of their efforts, bacteria became the main source of information about genetic control of biochemical processes in the cell. Tatum, Beadle, and Lederberg shared the Nobel Prize in 1958.