Everything about Polar Body totally explained
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, whereas the second polar body contains only one
chromatid 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 doesn't disintegrate and is fertilized by a
sperm; but such development would usually be impossible because it doesn't 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's 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.
Additional images
Image:Gray5.svg|Diagram showing the reduction in number of the chromosomes in the process of maturation of the ovum.
Image:Gray7.png|Scheme showing analogies in the process of maturation of the ovum and the development of the spermatids.
Image:Gray8.png|The process of fertilization in the ovum of a mouse.
Further Information
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