The work of American geneticist George Beadle (1903–1989) and American geneticist Edward Tatum (1909–1975) in the 1930s and 1940s demonstrated the relationship between genes and proteins. They grew the orange bread mold Neurospora on a specific growth medium. After exposing the mold to ultraviolet (UV) radiation, the mold was unable to grow on a medium unless it was supplemented with specific amino acids. The UV radiation caused a single gene mutation that led to the production of a mutant enzyme. This enzyme, in turn, caused the mold to exhibit a mutant phenotype. Beadle and Tatum’s work was important in demonstrating that genes control phenotypes through the action of proteins in metabolic pathways. In other words, one gene affects one enzyme. Since Beadle and Tatum were awarded their Nobel Prize in 1958, scientists have discovered that the relationship between genes and their proteins is much more complex.