Oogenesis
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Oogenesis is the creation of an ovum (egg cell) in the ovarian follicle of the ovary. Oogenesis is not to be confused with oocytogenesis, which is the formation of oocytes, which are the female gametocytes that divide later into ova.
In mammals, oogonial transformation into oocytes (oocytogenesis) is completed either before or shortly after birth. The further development comes to a rest during prophase I of meiosis until puberty. In Ascaris, the oocyte does not even begin meiosis until the sperm touches it.
In meiosis, the oocyte divides in four, of which only one becomes an ovum, the others becoming polar bodies. There may be two polar bodies, in which case one is diploid and did not undergo meiosis II.
See also: spermatogenesis, folliculogenesis