DEVELOPMENT AND MALDEVELOPMENTGAMETOGENESIS

The production of ova and sperm occurs via the process of meiosis (whereas somatic cells undergo division via mitosis). Oogenesis produces ova, and spermatogenesis produces sperm. One spermatogonium results in four sperm, and one oogonium results in one ovum and two polar bodies. Meiosis is a reduction division normally allowing each gamete to contain 23 chromosomes (haploid). Thus, when fertilization occurs and the two haploid gametes unite, the resulting zygote contains 46 chromosomes (diploid) under normal circumstances. Two meiotic divisions occur, and each contains several stages. ...