Recombination between homologous chromosomes is completed by the end of

Options

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

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks about the stage in meiosis when recombination between homologous chromosomes is completed.

2. **Identifying the Stages of Prophase I**: Prophase I of meiosis consists of several stages: leptotene, zygotene, pachytene, and diplotene. Each stage has distinct characteristics.

3. **Analyzing Each Stage**:
- **Leptotene**: This is the initial stage where chromosomes begin to condense and become visible. However, recombination has not yet occurred.
- **Zygotene**: In this stage, homologous chromosomes begin to pair up in a process called synapsis, forming bivalents. However, crossing over has not yet been completed.
- **Pachytene**: This is the stage where recombination (crossing over) occurs. The chromosomes are clearly visible as tetrads, and recombination nodules appear, indicating sites of genetic material exchange.
- **Diplotene**: In this stage, the homologous chromosomes begin to separate but remain connected at the sites where crossing over occurred. By this stage, crossing over is completed.

4. **Conclusion**: Based on the analysis, recombination between homologous chromosomes is completed by the end of the **pachytene** stage.

5. **Final Answer**: The correct option is **pachytene**.