In a young temale ot reproductive age with regular menstrual cycles of 28 days, ovulation occurs around 14lh day ot periods. When is the tirst polar body extruded ?
Accompanied by ovulation Most of the standard text books say the first polar body is expelled just before or sholy before ovulation. -- Which does not mean that it is released 24 hrs before ovulation. "While still in the ovary the ovum is in the primary oocyte stage. Sholy before it is released from ovarian follicle (i.e. sholy before ovulation), its nucleus divides by meiosis and a first polar body is expelled from the nucleus of the oocyte. The primary oocyte then becomes the secondary oocyte. In this process each of the 23 unpaired of chromosomes loses one of its paners which become the first polar body that is expelled. This leaves 23 unpaired chromosomes in the secondary oocyte. It is at this time that the ovum, still in the secondary oocyte stage is ovulated into the abdominal cavity." first polar body is released at the time of ovulation i.e. Option : b Note : - The secondary oocyte immediately begins the second meiotic division, but this division stops at metaphase and is completed only when sperm penetrates the oocyte. At this time second polar body is cast off. So second polar body is cast off at the time of feilization. Extra Edge : Friends this is an often repeated question and those who find it difficult to remember this basic fact: I have a mnemonic : Mnemonic PP1 and M2F PP1 i.e. 1st meiotic division is arrested in Prophase and completed just prior to ovulation releasing the 1st polar body M2F : i.e. 2nd meiotic division is arrested in metaphase and completed at the time of feilisation releasing the 2nd polar body
24 hrs prior to ovulation
Accompanied by ovulation
48 hrs after the ovulation
At the time of feilization