| Citation | Siminovitch's first major contribution to biology was to demonstrate, with Lwoff, that prophages could be induced by ultraviolet light. His further work on bacteriophages included the isolation of a large spectrum of bacteriophage lamda mutants that affect morphogenesis and the exploitation of these mutants to delineate, for the first time, nearly all of the proteins involved in lamda morphogenesis. Turning to the study of somatic mammalian cells, he developed methods for culturing such cells in suspension and for their karyotypic analysis by the air-drying technique. He demonstrated that there was little turnover of DNA in cell cultures growing logarithmically under controlled conditions. He was closely involved in the development of the spleen colony method for studying haemopoiesis and he showed that the differentiation of blood cells occurs by stochastic processes that can be affected by mutations involving either the stem cells themselves or the host. In recent years he has made important contributions to somatic cell genetics, especially in the isolation and study of conditional lethal mutants. His department at the University of Toronto is one of the world's leading centres for the study of mammalian cells. |