Ly·sen·ko \lə-ˈseŋ-kō\ , Trofim Denisovich (1898–1976), Soviet biologist and agronomist. Lysenko was the virtual dictator of biology in the Soviet Union from the 1930s through the early 1960s. He was Director of the Institute of Genetics of the Academy of Sciences of the United StatesS.R. from 1940 to 1965. His biological theories came to be officially adopted and mandated throughout the Soviet Union despite their virtually total rejection elsewhere. He attacked Mendelian genetics and advocated a revised form of Lamarckism, the doctrine of the inheritance of acquired characteristics. He denied the existence of genes and plant hormones and asserted that all parts of an organism have a role in heredity. He held that the application of his genetic theories would result in the development of new types of crops and increased agricultural production. In the face of overwhelming scientific challenges and the ultimate loss of political support, he was stripped of all authority in 1965 and his doctrines were repudiated.