American biochemist and geneticist (1928-) who developed the Ames test for chemical mutagens.Ames, Bruce N.: American biochemist and geneticist (1928-) who developed the Ames test for chemical mutagens.Ames attended Cornell University from 1946 to 1950, receiving his B.A. degree in chemistry/biochemistry. He then moved to the California Institute of Technology for his graduate study under Herschel K. Mitchell, a former postdoctoral fellow of George Beadle, in the biology department. Ames worked on the biosynthesis of histidine in Neurospora. After taking his Ph.D. within three years, he came to the National Institute of Arthritis and Metabolic Diseases in 1953 as a Public Health Service fellow. There he isolated the enzymes involved in the histidine pathway, and began to work on gene regulation in histidine biosynthesis using Salmonella. Collaborating with Philip Hartman of the Johns Hopkins University, Ames showed that the histidine genes could be overexpressed if histidine availability limited the growth rate. He also demonstrated that the cluster of genes was controlled together as a unit by a regulatory sequence. In 1962, Ames became a section head in the newly created laboratory of molecular biology led by Gordon Tomkins. Ames is perhaps best known for the "Ames test," the test he developed for chemical mutagens. Mutagens are agents that tend to increase the frequency or extent of genetic mutation. The Ames test, which uses a rapid and inexpensive bacterial assay for mutagenicity, complements epidemiologic surveys and animal tests that are necessarily slower, more laborious, and far more expensive. Ames began to work on this test in 1964, and after moving to the University of California, Berkeley, as professor of biochemistry in 1967, he continued to improve the sensitivity of the test. The Ames test has been used extensively to help evaluate the mutagenic and carcinogenic risks of a large number of chemicals. In the 1980s, Ames' research interest shifted to the question of aging and showed the role of mitochondrial decay as a major contributor to aging and age-related degenerative diseases. He is a recipient of the National Medal of Science and a member of the National Academy of Sciences.