Question

Meiotic division of the secondary oocyte is complete

• A. Prior to ovulation
• B. At the time of copulation
• C. After zygote formation
• D. At the time of fusion of a sperm with an ovum

Answer 1

The Correct Option is D

To understand when the meiotic division of the secondary oocyte is completed, we need to delve into the process of oocyte maturation and fertilization in humans.

The process begins with the primary oocyte, which is arrested at the Prophase I stage of meiosis during a female's fetal development. At puberty, follicles start to mature with each menstrual cycle, and one is typically selected to continue meiosis.

Meiotic Stages of Oogenesis:

1. Primary Oocyte: Remains arrested in Prophase I until the female reaches puberty.
2. Secondary Oocyte: Meiosis I is completed in the Graafian follicle, resulting in a secondary oocyte and a polar body. The secondary oocyte begins Meiosis II but is arrested at Metaphase II.
3. Completion of Meiosis II: The secondary oocyte only completes Meiosis II after fertilization, when a sperm penetrates the oocyte. This results in the formation of the ovum and another polar body.

Therefore, the meiotic division of the secondary oocyte is completed at the time of fusion of a sperm with an ovum, not before ovulation or simply post-zygote formation without fertilization.

Why Other Options are Incorrect:

• Prior to ovulation: Meiosis II begins but is not completed at this stage.
• At the time of copulation: Copulation does not guarantee fertilization; hence, meiosis II remains incomplete without sperm fusion.
• After zygote formation: The zygote forms only after meiosis II is completed, not before.

Conclusion: Thus, the correct answer is that the meiotic division of the secondary oocyte is complete at the time of fusion of a sperm with an ovum.