Polar body

Polar body

A polar body is a cell structure found inside an ovum. Both animal and plant ova possess it. Asymmetrical cell division (cytokinesis) leads to the production of polar bodies during oogenesis. To conserve nutrients, the majority of cytoplasm is segretated into either the secondary oocyte or ovum, during meiosis I or meiosis II, respectively. The remaining daughter cells generated from the meiotic events contain relatively little cytoplasm and are referred to as polar bodies. Eventually, the polar bodies degenerate.

There may be one or two polar bodies in the ovum of plant or possibly animal cells possess it.The first polar body is one of the two products in the first stage of meiosis and is diploid, with 46 chromatids (2x23), whereas the second polar body contains only one of each chromatid, (23 chromatids) and is haploid. Both are relatively small and contain little cytoplasm. Sometimes the first polar body undergoes the second meiotic cell division.

Some say that this second polar body can potentially result in half-identical twins, when the second polar body does not disintegrate and is fertilized by a sperm; but such development would usually be impossible because it does not have enough cytoplasm (and yolk, if the ovum has yolk) to feed the developing embryo.

In plants, the pollen releases two male gametes (sperm nuclei) into the ovule upon fertilization. One fertilizes the haploid ovum and develops into a normal embryo, while the other fertilizes the two polar bodies within the center of the ovary, creating a structure called endosperm. Endosperm stores nutrients for initial growth of plant seeds. Cereal grain is an example of this, and is consumed for its nutritional value by many animals, including humans.

Polar bodies are the by-products of the egg’s division during meiosis. As an egg matures, it goes through a two-step division process, dividing once at the time when ovulation would occur and again at the time of fertilization. The two polar bodies are the by-products of this division, and are essentially being discarded by the egg. By analyzing the polar bodies, it is possible to infer the genetic status of the egg. Therefore, polar body analysis allows us to test the mother’s genetic contribution to the embryo.


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Look at other dictionaries:

  • Polar body — Polar Po lar, a. [Cf. F. polaire. See {Pole} of the earth.] 1. Of or pertaining to one of the poles of the earth, or of a sphere; situated near, or proceeding from, one of the poles; as, polar regions; polar seas; polar winds. [1913 Webster] 2.… …   The Collaborative International Dictionary of English

  • polar body — n a cell that separates from an oocyte during meiosis: a) one containing a nucleus produced in the first meiotic division called also first polar body b) one containing a nucleus produced in the second meiotic division called also second polar… …   Medical dictionary

  • polar body — polar body. См. полярное тельце. (Источник: «Англо русский толковый словарь генетических терминов». Арефьев В.А., Лисовенко Л.А., Москва: Изд во ВНИРО, 1995 г.) …   Молекулярная биология и генетика. Толковый словарь.

  • polar body — n. a minute cell cast off when a primary oocyte undergoes meiotic division to produce a secondary oocyte and again when the secondary oocyte divides to produce an ovum …   English World dictionary

  • polar body — In animals each meiotic division of the oocyte leads to the formation of one large cell (the egg) and a small polar body as the other cell. Polar body formation is a consequence of the very eccentric position of the nucleus and the spindle …   Dictionary of molecular biology

  • polar body — noun Date: 1888 a cell that separates from an oocyte during meiosis and that contains a nucleus produced in the first or second meiotic division and very little cytoplasm …   New Collegiate Dictionary

  • polar body — A minute, functionless cell produced and discarded during the development of an oocyte …   Dictionary of invertebrate zoology

  • polar body — Cell Biol. one of the minute cells arising from the unequal meiotic divisions of the ovum at or near the time of fertilization. [1885 90] * * * …   Universalium

  • polar body — noun One of the small cells that are by products of the meiosis that forms an egg …   Wiktionary

  • polar body — noun Biology each of the small cells which bud off from an oocyte at the two meiotic divisions and do not develop into ova …   English new terms dictionary

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