Beadle and Tatum's key experiments involved exposing the bread mold Neurospora crassa to x-rays, causing mutations. In a series of experiments, they showed that these mutations caused changes in specific enzymes involved in metabolic pathways. These experiments, published in 1941, led them to propose a direct link between genes and enzymatic reactions, known as the "one gene, one enzyme" hypothesis.
Tatum was born in Boulder, Colorado. He attended the college at the University of Chicago for two years, and transferred to the University of Wisconsin–Madison, where he received his BA in 1931 and PhD in 1934. Starting in 1937, he worked at Stanford University, where he began his collaboration with Beadle. He then moved to Yale University in 1945 where he mentored Lederberg. He returned to Stanford in 1948 and then joined the faculty of Rockefeller Institute in 1957. A heavy cigarette smoker, he died in New York City of heart failure complicated by chronic emphysema.
