Lewis, Edward B (1918-2004)

US geneticist who was awarded a Nobel Prize for Physiology or Medicine in 1995 with Eric F Wieschaus and Christiane Nusslein-Volhard for their discovery of genes which control the early stages of the body's development.

Lewis at the California Institute of Technology, Pasedena, USA, began research on the development of the fruit fly in 1946. He bred generation after generation of flies, looking for rare mutations called homeotic transformations which caused one body part to substitute for another in the adult fly. For instance, one such mutation causes the body segment which usually bears tiny balancing organs called halteres to be replaced by a second pair of wings. Lewis found that many of the genes causing homeotic transformations were grouped into a single cluster on one chromosome. Within this cluster, the genes were neatly ordered: genes affecting the abdomen were at one end, and those affecting the head were at the other end. Similar principles are now known to control the development of other species, including humans.