Recombination between homologous chromosomes completed by the end of:

Options

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

Answer

**Step-by-Step Solution:**

1. **Understanding Recombination**: Recombination is a process that occurs during meiosis where genetic material is exchanged between homologous chromosomes. This leads to genetic diversity in the resulting gametes.

2. **Meiosis Overview**: Meiosis is a type of cell division that reduces the chromosome number by half, creating four haploid cells from one diploid cell. It consists of two main stages: Meiosis I and Meiosis II.

3. **Phases of Meiosis I**: The first stage of meiosis, Meiosis I, includes several phases: Prophase I, Metaphase I, Anaphase I, and Telophase I. The focus here is on Prophase I, which is further divided into several substages.

4. **Prophase I Substages**:
- **Leptotene**: Chromosomes begin to condense.
- **Zygotene**: Homologous chromosomes pair up in a process called synapsis.
- **Pachytene**: This is the key stage for recombination. During this phase, crossing over occurs between non-sister chromatids of homologous chromosomes.

5. **Crossing Over**: In the Pachytene stage, segments of DNA are exchanged between non-sister chromatids, leading to the formation of recombinant DNA. This is crucial for genetic variation.

6. **Conclusion**: The process of recombination between homologous chromosomes is completed by the end of the Pachytene stage of Prophase I in meiosis.

**Final Answer**: Recombination between homologous chromosomes is completed by the end of the Pachytene stage.

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