born May 20, 1918, Wilkes-Barre, Pa., U.S.
died July 21, 2004, Pasadena, Calif.
U.S. geneticist.
He received a Ph.D. (1942) in genetics from the California Institute of Technology, where he taught from 1946 to 1988. By crossbreeding thousands of fruit flies, he discovered that genes are arranged on the chromosome in the order corresponding to body segments, an orderliness now known as the colinearity principle. Lewis's work helped explain mechanisms of general biological development, including the causes of deformities present at birth in humans. With Christiane Nüsslein-Volhard and Eric F. Wieschaus, he was awarded a 1995 Nobel Prize.