In spermatogenesis, reduction division of chromosomes occurs during conversion of

Options

A. spermatogonia to primary spermatocytes
B. primary spermatocytes to secondary spermatocytes
C. secondary spermatcytes to spermatids
D. spermatids to sperms

Answer

To solve the question regarding the reduction division of chromosomes during spermatogenesis, we can break it down into the following steps:

### Step-by-Step Solution:

1. **Understanding Spermatogenesis**:
- Spermatogenesis is the process of sperm formation that occurs in the seminiferous tubules of the testes. It involves several stages of cell division and differentiation.

2. **Starting Point - Spermatogonia**:
- The process begins with primordial germ cells that develop into spermatogonia. Spermatogonia are diploid cells (2n), meaning they contain two sets of chromosomes.

3. **Mitosis of Spermatogonia**:
- Spermatogonia undergo mitotic divisions to produce primary spermatocytes. Since mitosis does not reduce the chromosome number, primary spermatocytes also remain diploid (2n).

4. **First Meiotic Division**:
- Primary spermatocytes undergo the first meiotic division (meiosis I). This is the crucial step where reduction division occurs. During meiosis I, the chromosome number is halved, resulting in the formation of secondary spermatocytes, which are haploid (n).

5. **Formation of Spermatids**:
- Secondary spermatocytes then undergo the second meiotic division (meiosis II), resulting in spermatids. However, this step does not involve a reduction in chromosome number, as the cells are already haploid.

6. **Final Development into Sperm**:
- Finally, spermatids mature into spermatozoa (sperm). This maturation process does not involve further reduction in chromosome number.

### Conclusion:
- The reduction division of chromosomes occurs during the conversion from **primary spermatocytes to secondary spermatocytes**.

### Answer:
- The correct option is **B: Primary spermatocyte to secondary spermatocyte**.

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