ABSTRACT
Several checkpoint mechanisms that regulate the different stages of male meiosis can eliminate defective germ cells and ensure spermatozoa with a normal chromosome content. For this reason, spermatogenesis can be partially arrested in any of the maturation stages, resulting in oligozoospermia (reduced sperm number), or it can be completely arrested, resulting in azoospermia (absence of sperm). However, if these control mechanisms are deficient, any of the abnormal cell lines can evade the checkpoints and give rise to chromosomally abnormal spermatozoa.
