Question

Extrusion of second polar body from egg nucleus occurs

• A. After entry of sperm before completion of fertilization.
• B. After completion of fertilization.
• C. Before entry of sperm.
• D. Without any relation of sperm entry.

Answer 1

The correct option is A After entry of sperm before completion of fertilization.

The secretions of the acrosome help the sperm enter into the cytoplasm of the ovum through the zona pellucida and the plasma membrane. This induces the completion of the meiotic division of the secondary oocyte. The second meiotic division is also unequal as the first meiotic division and results in the formation of a second polar body and a haploid ovum (ootid). Soon after separation of second polar body the haploid nucleus of the sperms and that of the ovum fuse together to form a diploid zygote.