George Beadle

George Beadle was an American geneticist who, working with Edward Tatum in the early 1940s, developed the one gene, one enzyme hypothesis, the proposal that each gene functions by directing the production of a single specific enzyme. Beadle and Tatum exposed the bread mold Neurospora crassa to X-rays to induce mutations, then identified mutant strains that had lost the ability to produce specific nutrients on their own, showing that each mutation disrupted one particular biochemical step in an orderly metabolic pathway, and that each step corresponded to a single gene. This work provided one of the first direct experimental links between genes, understood at the time mainly as abstract units of inheritance, and the concrete biochemical machinery of the cell, helping to found the field of biochemical genetics. Beadle later served as president of the California Institute of Technology and then the University of Chicago, and he shared the 1958 Nobel Prize in Physiology or Medicine with Edward Tatum and Joshua Lederberg for their discoveries concerning the genetic regulation of chemical processes.