The project is designed to study the effects of chromosomal aberrations on fetal mortality and development. Comparisons will be made between in vivo effects and effects on mouse embryos grown in culture. Chemicals mutagens are known to be capable of inducing chromosomal aberrations such as translocations which may be transmitted to the next generation. Increased rates of fetal death are usually observed among offspring to translocation heterozygotes. It is our purpose to investigate the transmission of such aberrations, and the processes of fetal mortality by direct observation of the development of embryos.