Relatively longer and complex stage of prophase-I

Options

A. Leptotene
B. Diplotene
C. Zygotene
D. Pachytene

Answer

**Step-by-Step Solution:**

1. **Understanding Prophase I**: Prophase I is a crucial stage of meiosis, which is a type of cell division that reduces the chromosome number from diploid (2n) to haploid (n). This stage is known for its complexity and duration compared to other stages of meiosis.

2. **Sub-stages of Prophase I**: Prophase I is divided into five sub-stages:
- Leptotene
- Zygotene
- Pachytene
- Diplotene
- Diakinesis

3. **Identifying the Longest and Most Complex Stage**: Among these five sub-stages, the pachytene stage is recognized as the longest and most complex. This complexity arises due to the significant events that occur during this phase.

4. **Crossing Over**: The pachytene stage is particularly important because it is during this stage that crossing over occurs. Crossing over is the exchange of genetic material between non-sister chromatids of homologous chromosomes, leading to genetic recombination. This process is essential for genetic diversity.

5. **Conclusion**: Given the options provided (leptotin, zygotin, pachytene, diplotin), the correct answer to the question about the relatively longer and complex stage of prophase I is **pachytene**.

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