Question

The second maturation division of the mammalian ovum occurs

• A. Until after the ovum has been penetrated by a sperm
• B. Until the nucleus of the sperm has fused with that of the ovum
• C. In the Graafian follicle following the first maturation division
• D. Shortly after ovulation before the ovum makes entry into the fallopian tube

Answer 1

The correct option is A

Until after the ovum has been penetrated by a sperm

The correct option is A.

Explanation of the correct option:

1. The primary oocyte develops and completes meiosis I (first maturation division) during oogenesis, resulting in the formation of a secondary oocyte and a small polar body.
2. The second maturational division (meiosis II) of the secondary oocyte continues, however it is stopped at the metaphase stage.
3. The ovum completes its meiosis II after its penetration by the sperm.

Explanation of the incorrect option:

Option B:

The fusion of the nucleus of sperm and ovum occurs after the maturation of the ovum ( after the completion of meiosis II ).

Option C:

1. The mature follicle called Graafian follicle ruptures to release the secondary oocyte.
2. The secondary oocyte reaches the fallopian tube and completes meiosis II to become a mature ovum.

Option D:

The secondary oocyte reaches the fallopian tube and if it does not comes in contact with sperm, it will not complete its meiosis to become a mature ovum.

Final answer: The second maturation division of the mammalian ovum occurs after the ovum has been penetrated by a sperm.