Meiosis in mammals: recombination, non-disjunction and the environment.

By comparison with other species, the meiotic process in the human female is extraordinarily error-prone. In addition to the well-known effect of advancing maternal age, recent studies have demonstrated that the number and location of meiotic recombination events influences the likelihood of meiotic non-disjunction in our species. Although this association extends to many other organisms, the factors that influence the number and placement of exchanges within a cell remain poorly understood. Like other aspects of meiosis, the control of recombination is likely to be subject to variation among species. In this review we summarize data from recent studies in mammals; the combined data suggest that both genetic and environmental factors influence recombination in mammals and, importantly, that control mechanisms probably differ between males and females.