Edward Tatum

Proposed by Edward Tatum and George Beadle in the 1940s, the hypothesis states that each gene directs the synthesis of a single enzyme, thereby controlling one step in a biochemical pathway. They developed this idea through experiments with the bread mold Neurospora crassa, showing that mutations knocking out specific genes led to the loss of specific enzymatic functions. This was a foundational concept linking genetics to biochemistry.

Tatum and Beadle used the orange bread mold Neurospora crassa, a fungus that could grow on minimal medium containing only sugar, inorganic salts, and biotin. By exposing Neurospora to X-rays to create mutations and then testing which strains required specific amino acid or vitamin supplements, they mapped genes to biochemical pathways. This system was ideal because Neurospora's simple nutritional requirements made metabolic defects easy to detect.

Tatum shared the 1958 Nobel Prize in Physiology or Medicine with his collaborator George Beadle, then at Caltech, and with Joshua Lederberg, who was recognized separately for his discoveries on genetic recombination in bacteria. Beadle and Tatum received half the prize jointly for their one gene–one enzyme work, and Lederberg received the other half.

Tatum carried out his pivotal Neurospora experiments with Beadle at Stanford University in the early 1940s before moving to Yale University. At Yale, he and Joshua Lederberg demonstrated genetic recombination in bacteria, work that contributed to Lederberg's share of the 1958 Nobel Prize. Tatum later returned to Stanford before finishing his career at the Rockefeller Institute.