George Wells Beadle (October 22, 1903 – June 9, 1989) was an American geneticist.
He won the Nobel Prize in Physiology or Medicine with Edward Tatum; they shared the prize with Joshua Lederberg, who worked with Tatum on bacterial genetics.
Beadle and Tatum discovered the role of genes in regulating biochemical synthesis in cells.
Beadle and Tatum's key experiments involved exposing the bread mould Neurospora crassa to x-rays, causing mutations. In a series of experiments, they showed that these mutations caused changes in specific enzymes involved in pathways making proteins. They proposed a direct link between genes and enzymatic reactions, known as the "one gene, one enzyme" hypothesis.