Meiosis and Ageing in Mammals.

Meiosis is a specialized form of cell division that plays an essential role in mammalian sexual reproduction to reduce the ploidy of the developing germ cells so that each gamete transmits one copy of each chromosome to the next generation. In humans, approximately 20% of conceptions inherit the wrong number of chromosomes, with the vast majority of these aneuploid embryos arising from de novo chromosome segregation errors during meiosis. These inherited autosomal aneuploidies usually arise maternally during oocyte meiosis, and are strongly affected by maternal age. Paternally-inherited autosomal aneuploidies occur less frequently, and are also affected by age. Depending on the specific chromosome involved, aneuploid human embryos typically die before implantation, are miscarried, or develop genetic disorders such as Down syndrome. Despite the significant impact of inherited aneuploidies on the incidence of human genetic disease and reproductive outcomes, the molecular mechanisms through which ageing impacts on the fidelity of meiotic chromosome segregation in mammals remain poorly understood. This review will outline some of the effects that ageing is thought to have on meiotic mammalian chromosomes to perturb meiotic chromosome segregation and impact on the incidence of inherited aneuploidies.