Question

Extrusion of second polar body from egg nucleus occurs
A) After entry of sperm but before fertilisation
B) After fertilisation
C) Before entry of sperm into ovum
D) Simultaneously with first cleavage

Answer 1

A cell separates from the oocyte during meiosis. Two polar bodies are formed. The cell formed as a result of second meiotic division is called the second polar body. It contains a nucleus.

Complete answer:
A polar body is a small haploid cell which is formed as an egg cell during oogenesis. The polar body is the resultant structure that an egg produced after meiosis. It results in two cells. One cell has the majority of cytoplasm while the other cell is small. The smaller cell is called the first polar body which generally disintegrates. The resultant larger ovum cell undergoes meiosis and produces a second polar body. This polar body undergoes meiosis and forms egg cells. The sperm entry activates the metaphase promoting factor and then the sperm enters fertilisation. Thus the extrusion of the second polar body occurs after the entry of sperm but before fertilisation.

Thus the correct answer is option (A).

Additional Information The quality of the polar body like its morphology can be used to see the oocyte viability and also predict the fertilisation rates and pregnancy achievement.

Note: The secondary oocyte commences meiosis II which gets arrested at metaphase. It will not continue without fertilisation. Thus the eggs from the secondary polar body are released before fertilisation.