Wieschaus, Eric Francis, 1947–, American biologist and geneticist, b. South Bend, Ind., Ph.D. Yale 1974. He was a researcher at the European Molecular Biology Laboratory in Heidelberg, Germany, from 1978 to 1981, when he joined the faculty at Princeton. Wieschaus shared the 1995 Nobel Prize in Physiology or Medicine with Christiane Nüsslein-Volhard and Edward B. Lewis for their discoveries concerning the genetic control of early embryonic development. Using the fruit fly, Drosophila melanogaster, as their experimental system, Wieschaus and Nüsslein-Volhard identified and classified a group of genes that play a key role in determining the overall body plan as well as the formation of body segments. Their work provided the foundation for Lewis to elucidate how individual segments develop into specific organs; the combined work of the three offered important new insights into the process of evolution and laid the groundwork for understanding congenital defects in humans.