Chromosome number is halved during

Options

A. Formation of first polar body
B. Formation of second polar body
C. Meiosis II
D. Division of secondary oocyte.

Answer

**Step-by-Step Solution:**

1. **Understanding Chromosome Number**:
- Human cells typically have 46 chromosomes, arranged in 23 pairs. This is referred to as the diploid number (2n).

2. **Identifying the Process**:
- The question asks when the chromosome number is halved. This occurs during a specific type of cell division known as meiosis.

3. **Meiosis Overview**:
- Meiosis consists of two main divisions: Meiosis I and Meiosis II. The first meiotic division (Meiosis I) is crucial for reducing the chromosome number.

4. **Primary Oocyte**:
- In females, the primary oocyte is the cell that undergoes meiosis. A primary oocyte contains 46 chromosomes (diploid).

5. **Meiosis I - Formation of Secondary Oocyte and Polar Body**:
- During Meiosis I, the primary oocyte divides into two cells: a secondary oocyte and a polar body.
- The secondary oocyte retains most of the cytoplasm and is haploid (23 chromosomes), while the polar body is a smaller cell that usually does not participate in further development.

6. **Conclusion**:
- Since the primary oocyte (46 chromosomes) divides into a secondary oocyte (23 chromosomes) and a polar body (23 chromosomes), the chromosome number is halved during this process.
- Therefore, the correct answer to the question is that the chromosome number is halved during the formation of the first polar body.

**Final Answer**: The chromosome number is halved during the formation of the first polar body.

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