The second maturation division of the mammalian ovum occurs

Options

A. (a) in the graffian follicle following the first maturation division
B. (b) shortly after ovulation before the ovum makes entry into the fallopian tube
C. (c) until after the ovum has been penetrated by a sperm
D. (d) until the nucleus of the sperm has fused with ovum

Answer

**Step-by-Step Solution:**

1. **Understanding Oogenesis**: Oogenesis is the process of producing ova (egg cells) in mammals. It begins with primordial germ cells that develop into oogonia.

2. **Formation of Primary Oocyte**: The oogonia undergo mitosis to produce primary oocytes. These primary oocytes are diploid (2n) and are arrested in prophase I of meiosis until puberty.

3. **First Maturation Division**: At puberty, during the menstrual cycle, primary oocytes complete the first meiotic division, resulting in a secondary oocyte and a first polar body. The secondary oocyte is haploid (n) and is released during ovulation.

4. **Arrested Metaphase**: The secondary oocyte undergoes the second meiotic division but is arrested at metaphase II. This means it will not complete this division until fertilization occurs.

5. **Fertilization**: When a sperm penetrates the secondary oocyte, it triggers the completion of meiosis II. This results in the formation of an ovum (the fertilized egg) and a second polar body.

6. **Conclusion**: The second maturation division of the mammalian ovum occurs immediately after the sperm penetrates the ovum, leading to the formation of the fertilized egg.

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

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