Oocyte

An oocyte, ovocyte, or rarely o÷cyte, is a female gametocyte or germ cell involved in reproduction. In other words, it is an immature ovum. An oocyte is part of the ovary development. The germ cells produce a primordial germ cell (PGC) which becomes an oogonia which marks the start of mitosis. After mitosis stops (due to actions of retinoic acid and the mesenephros) meiosis starts. This stage the oogonia is now an Oocyte (pronounced ''oh'a (like Noah)-site'').

Formation

The formation of an oocyte is called oocytogenesis, which is a part of oogenesis. Oogenesis results in the formation of both primary oocytes before birth, and of secondary oocytes after it as part of ovulation.

Cell type ploidy/chromosomes chromatids Process Time of completion
Oogonium diploid/46 2N Oocytogenesis (mitosis) third trimester
primary Oocyte diploid/46 4N Ootidogenesis (meiosis 1) (Folliculogenesis) Dictyate in prophase I until ovulation
secondary Oocyte haploid/23 2N Ootidogenesis (meiosis 2) Halted in metaphase II until fertilization
Ootid haploid/23 1N ? Minutes after fertilization
Ovum haploid/23 1N

Characteristics

Cytoplasm

Oocytes are rich in cytoplasm which contains yolk granules to nourish the cell early in development.

Nucleus

During the primary oocyte stage of oogenesis, the nucleus is called a germinal vesicle The only normal type of secondary oocyte has sex chromosomes 23,X (where sperm can be 23,X or 23,Y).

Nest

The space wherein an ovum or immature ovum is located is the cell-nest.

Abnormalities

Resources

William K. Purves, Gordon H. Orians, David Sadava, H. Craig Heller, Craig Heller (2003). Life: The Science of Biology(7th ed.), pp. 823–824

See also

External links

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This article is based on "Oocyte" from the free encyclopedia Wikipedia (http://en.wikipedia.org). It is licensed under the terms of the GNU Free Documentation Licencse. In the Wikipedia you can find a list of the authors by visiting the following address: http://en.wikipedia.org/w/index.php?title=Oocyte&action=history