Extrusion of second polar body from egg nucleus occurs :
- Before entry of sperm into ovum
- Simultaneously with first cleavage
- After entry of sperm but before fertilization
- After fertilization
Answer
(3) After entry of sperm but before fertilization
Solution
As per NCERT, the entry of the sperm into the ovum induces the completion of the meiotic division of the secondary oocyte.
⇒ This second meiotic division is unequal and results in the formation of a second polar body and a haploid ovum (ootid).
⇒ Soon after, the haploid nucleus of the sperm and that of the ovum fuse to form a diploid zygote (fertilisation).
∴ The second polar body is extruded after entry of the sperm but before fertilisation.
Answer: (3)