Chromosomes of the bivalent are fused (Joined) by their chiasmata near the telomeric ends during

Options

A. Pachytene
B. Zygotene
C. Metaphase-I
D. Anaphase-I

Answer

To solve the question regarding when the chromosomes of the bivalent are fused by their chiasmata near the telomeric ends, we can analyze the stages of meiosis, particularly focusing on prophase I, where these events occur.

### Step-by-Step Solution:

1. **Understand Meiosis**: Meiosis is a type of cell division that reduces the chromosome number by half, resulting in four haploid cells. It consists of two main stages: Meiosis I (reductional division) and Meiosis II (equational division).

2. **Identify Prophase I Substages**: Prophase I of meiosis is divided into five substages:
- Leptotene
- Zygotene
- Pachytene
- Diplotene
- Diakinesis

3. **Analyze Each Substage**:
- **Leptotene**: Chromosomes become visible, but no pairing occurs.
- **Zygotene**: Homologous chromosomes begin to pair through a process called synapsis, but chiasmata are not formed yet.
- **Pachytene**: Crossing over occurs, leading to the formation of chiasmata, but these are not yet at the telomeric ends.
- **Diplotene**: Chiasmata become visible, but they are still not terminalized at the telomeric ends.
- **Diakinesis**: Chiasmata terminalization occurs, meaning that the chiasmata move towards the telomeric ends of the chromosomes.

4. **Determine the Correct Stage**: The question specifically asks when the chromosomes of the bivalent are fused by their chiasmata near the telomeric ends. This occurs during **Metaphase I**, as the chiasmata are now positioned at the ends of the chromosomes.

5. **Conclusion**: Therefore, the correct answer to the question is **Metaphase I**.

### Final Answer:
The chromosomes of the bivalent are fused (joined) by their chiasmata near the telomeric ends during **Metaphase I**.

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