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Oogenesis or rarely oögenesis is the creation of an ovum (egg cell) in the ovarian follicle of the ovary.

In mammals, oogonial transformation into oocytes (oocytogenesis) is completed either before or shortly after birth. Further development comes to a rest during prometaphase I of meiosis, known as the Dictyate stage, until puberty triggers oogenesis. In Ascaris, the oocyte does not even begin meiosis until the sperm touches it.

Oogenesis is the process in which the primary oocyte turns to an ovum undergoing meiosis. At first you start with a diploid oocyte called the primary oocyte. Meiosis I occurs in which synapsis occurs and tetrads form and crossing over as well and this becomes the secondary oocyte and the first polar body. Then the secondary oocyte undergoes meiosis II and is a haploid called ootid and also a second polar bodies as well as the first polar bodies that undergoes meiosis II as well and turns into two more polar bodies making a total of 3 polar bodies that disintegrate leaving only the ootid which under goes maturation and turns to the ovum.

It is interesting to note that such an important process in animal life cycles is done completely without the aid of spindle-coordinating centrosomes.

See also

• Spermatogenesis

External links

• http://distance.stcc.edu/AandP/AP/AP2pages/reprod/oogenesi.htm
• Reproductive Physiology

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