1903-1989

American biologist who shared the Nobel Prize in physiology or medicine with Edward Tatum for the research that established the "one gene one enzyme" theory. Beadle and Tatum irradiated the common bread mold, Neurospora, and collected mutants that could no longer synthesize the amino acids and vitamins needed for growth. They then identified the steps in the metabolic pathways that had been affected by the mutations, establishing the relationship between mutant genes and defective enzymes.