Beadle and Tatum learn that mutations inactivate proteins.

In 1902, Archibald Garrod described the inherited disorder alkaptonuria as an "inborn error of metabolism." He proposed that a gene mutation causes a specific defect in the biochemical pathway for eliminating liquid wastes. The phenotype of the disease — dark urine — is a reflection of this error. This hypothesis was rigorously proven in 1941 by George Beadle and Edward Tatum, using the simple bread mold Neurospora. First, they found that molds exposed to radiation lose the ability to produce essential nutrients, and this slowed, even stopped the growth of the mold. Then, they found that growth can be restored by providing the mutated mold with a specific supplement. They reasoned that each mutation must inactivate the enzyme (protein) needed to synthesize the nutrient. Thus, one gene carries the directions for making one protein.

george beadle and edward tatum, archibald garrod, inborn error of metabolism, bread mold, enzyme protein, gene mutation, biochemical pathway, alkaptonuria, dark urine, mutations, hypothesis, reflection, radiation