This proposal is a continuation of an ongoing program on the molecular aspects of the meiotic process in mammalian spermatocytes. It is a process which is critical to normal sperm development and also to normal genetic transmission. The main thrust of the research program is to clarify the biochemical factors which regulate and determine the mechanisms governing crossing-over between chromosomes. A substantial feature of the program derives from results obtained during the past two years in which it has been shown that a well defined metabolic program exists in the spermatocyte which is correlated with chromosome behavior meiosis and in which it has also been shown that two distinctive proteins are present in the spermatocytes that can either separate or reanneal DNA strands. By isolating spermatocytes at different stages of meiosis it is possible to examnie chromosomal constitution and protein activities of the spermatocytes as they develop to the spermatid stage. We wish to purify the two distinctively meiotic proteins and others related to them in order to determine their activities in the crossing over process. The behavior of these proteins will also be analyzed in connection with meiotic upsets that result in sterility. Chromosomes behavior will be examined from two standpoints: (1) Specific changes which occur in the structure of the chromosomes as related to their functioning in crossing-over. (2) Characterization of DNA sequences that are known to have special functions in meiosis. We also plan (in a collaborative effort) to determine the biochemical basis for sterility in male mice which have suffered translocations.