Gametogenesis - Human Development
Gametogenesis as you are responsive is the process of formation and development of specialized reproductive cells, ova in females and sperms in males. In this procedure the chromosome number is reduced by half in both sperms and ova. Any disturbance during gametogenesis for instance non-disjunction, results in abnormal development as seen in trisomy-21 and Down's syndrome. You should keep in mind that in humans, gametogenesis is a continuous process that starts at puberty. It is not a seasonal or periodic phenomenon as in several other animals including mammals.