In this photomicrograph of a human egg (from Simon Fishel) two polar bodies are visible at about 11 O'clock (under the cytoplasmic membrane and 'indenting' the cytoplasm. The presence of two polar bodies indicates that this egg has been fertilized.
A polar body is a small structure consisting mainly of genetic material but also some cytoplasm. It is emitted from the the egg (oocyte).
The 1st polar body is emitted at the end of the first meiotic division and contains a half of the genetic material of the egg.
The second polar body is not released until the second meiotic division is complete- usually as a response to the penetration of the spermatozoon - it contains haploid complement of chromosomes The result of the second emission is that the fertilized egg has a complement of 23 chromosome -half of the original 46 chromosomes. When fertilisation is complete and the two pronuclei have fused the chromosome complement returns to 46 - 23 from the egg and 23 from the sperm.
In this
photomicrograph of a human egg (from Simon Fishel) two polar bodies are visible
at about 11 O'clock (under the cytoplasmic membrane and 'indenting' the
cytoplasm. The presence of two polar bodies indicates that this egg has been
fertilized.