TONEGAWA SUSUMU

born Sept. 5, 1939, Nagoya, Japan Japanese molecular biologist who was awarded the Nobel Prize for Physiology or Medicine in 1987 for his discovery of the genetic mechanisms underlying the great diversity of antibodies produced by the vertebrate immune system. Tonegawa earned a B.S. degree from Kyoto University in 1963 and a Ph.D. in molecular biology from the University of California at San Diego, U.S., in 1969. He was a member of the Basel Institute for Immunology in Switzerland from 1971 to 1981. During that time Tonegawa applied the newly devised recombinant DNA techniques of molecular biology to immunology and began to tackle one of the greatest unsolved immunological questions of the day: how antibody diversity is generated. Prior to Tonegawa's discovery, it was unclear how a limited number of genesthere are believed to be about 100,000 in the human genomecould produce the total human antibody repertoire, which numbers in the trillions. According to Tonegawa's research, each antibody protein is not encoded by a specific gene, as one theory contended; instead, antibodies are constructed from a relatively small number of gene fragments that are rearranged randomly to generate different antibody molecules. In 1981 Tonegawa moved to the United States to become a professor of biology at the Center for Cancer Research at the Massachusetts Institute of Technology. In addition to conducting immunological investigations, Tonegawa studied molecular and cellular aspects of neurobiology and in 1994 became director of MIT's Center for Learning and Memory.