The central theme of this research program is reproductive biology with primary emphasis on gametogenesis. Each of the 3 component programs is concerned with investigating one or more aspects of reproduction in a particular organism. (1) Meiosis in rat spermatocytes will be analyzed biochemically to determine the constitution of nuclear membranes at prophase and also that of the synaptonemal complex in relation to chromosome pairing. Specific aspects of protein and DNA metabolism in spermatocytes at meiotic prophase will be studied from the standpoint of crossing-over. Efforts will be continued to improve conditions for culturing spermatocytes in vitro through the entire meiotic cycle. (2) Spermatogenesis in Drosophila will be analyzed by a combination of ultrastructural, biochemical, and genetical techniques. Special emphasis will be given to the kinetics of normal germ cell proliferation and development as a background for later identifying mutational lesions in spermiogenesis. Major attention will be given to histone alterations during spermiogenesis and to its relation to late nuclear condensation. Bulk isolation of larval testes for biochemical studies will be developed so as to make possible an analysis of nuclear constituents of meiotic cells. Improvements will be sought in culture techniques to extend the interval of spermatogenesis in vitro beyong the current limit of 36 hours. (3) The basis for genetically determined spontaneous parthenogenesis in mice will be studied with a view to determining whether the disposition to develop parthenogenetically arises from aberrations in the first or second meiotic division. The study will also be concerned with an analysis of the events that lead to an early death of the parthenogenone.