Lewis, Edward B.

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.

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▪ 2005

      American geneticist (b. May 20, 1918, Wilkes-Barre, Pa.—d. July 21, 2004, Pasadena, Calif.), discovered how certain genes control early development in embryos. For this work Lewis was awarded the 1995 Nobel Prize for Physiology or Medicine jointly with two other geneticists, Christiane Nüsslein-Volhard and Eric F. Wieschaus, whose independent research had complemented Lewis's studies. While on the faculty of the California Institute of Technology, Lewis studied the chromosomes of fruit flies for many years. He identified a group of genes that control development of the flies' body segments and found that the linear arrangement of the genes on the chromosome corresponds to the order of the body segments they control. He also discovered that the operation of these genes is turned on and off by a gene cluster that serves as a master control switch. Molecular biologists later determined that genes analogous to those identified by Lewis in fruit flies are present in most vertebrates (including humans) and that these genes control embryonic development in strikingly similar ways. In the mid-1950s Lewis conducted a landmark study on the effect of radiation as a source of cancer. His results challenged the U.S. government's position that there existed a level of radiation, called the threshold dose, below which a person could be safely exposed without cancer's being induced. Among the many honours Lewis accrued during his long career was election to the National Academy of Sciences (1968) and to the American Philosophical Society (1990). He became (1989) a foreign member of the Royal Society and was awarded (1990) the National Medal of Science.

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▪ American biologist

born May 20, 1918, Wilkes-Barre, Pennsylvania, U.S.

died July 21, 2004, Pasadena, California

      American developmental geneticist who, along with geneticists Christiane Nüsslein-Volhard (Nüsslein-Volhard, Christiane) and Eric F. Wieschaus (Wieschaus, Eric F.), was awarded the 1995 Nobel Prize for Physiology or Medicine for discovering the functions that control early embryonic (embryology) development.

      Lewis's interest in genetics was kindled in high school. He studied biostatistics at the University of Minnesota (B.A., 1939) and genetics at the California Institute of Technology (Ph.D., 1942), where he taught from 1946 to 1988. Working independently of Nüsslein-Volhard and Wieschaus, Lewis based his research on studies of the fruit fly, or vinegar fly (Drosophila melanogaster), a species popular for genetic experiments. By crossbreeding thousands of flies, he was able to establish that genes are generally arranged on the chromosome in the same order as their corresponding body segments—e.g., the first set of genes controls the head and thorax; the middle set, the abdomen; and the final set, posterior parts. This orderliness is known as the colinearity principle. Lewis also found that genetic regulatory functions may overlap. For example, a fly with an extra set of wings has a defective gene not in the abdominal region but in the thoracic region, which normally functions as a regulator of such mutations.

      Lewis's work on the fruit fly helped to explain mechanisms of general biological development, such as the causes of congenital deformities, in humans and other higher organisms. He was elected to the National Academy of Sciences in 1968 and received the National Medal of Science in 1990.

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