Recombination nodules which mediate for chromosome recombination occur during

Options

A. Zygotene
B. Meiosis
C. Pachytene stage
D. Diplotene stage

Answer

### Step-by-Step Solution

1. **Understanding Chromosome Recombination**:
- Chromosome recombination refers to the exchange of genetic material between non-sister chromatids of homologous chromosomes. This process is crucial for genetic diversity.

2. **Identifying the Context**:
- Recombination occurs during meiosis, which is the type of cell division that reduces the chromosome number by half and leads to the formation of gametes (sperm and eggs).

3. **Phases of Meiosis**:
- Meiosis consists of two main stages: Meiosis I and Meiosis II. Recombination specifically occurs during Meiosis I.

4. **Sub-stages of Meiosis I**:
- Meiosis I is divided into several phases: Prophase I, Metaphase I, Anaphase I, and Telophase I. The focus here is on Prophase I, which has several sub-stages.

5. **Sub-stages of Prophase I**:
- Prophase I includes five sub-stages: Leptotene, Zygotene, Pachytene, Diplotene, and Diakinesis.

6. **Identifying the Stage of Recombination**:
- Recombination nodules, which facilitate the exchange of genetic material, form during the Pachytene stage of Prophase I. This is when homologous chromosomes are closely aligned and exchange segments of DNA.

7. **Conclusion**:
- Therefore, the answer to the question is that recombination nodules, which mediate chromosome recombination, occur during the **Pachytene stage** of Prophase I in meiosis.

### Final Answer
Recombination nodules which mediate for chromosome recombination occur during the **Pachytene stage**.

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