At which stage, the homologous chromosomes separate due to repulsion, but are yet held by chiasmata?

Options

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

Answer

To answer the question, "At which stage do the homologous chromosomes separate due to repulsion, but are yet held by chiasmata?" we need to analyze the stages of meiosis, particularly during prophase I.

### Step-by-Step Solution:

1. **Understanding Meiosis**: Meiosis is a type of cell division that reduces the chromosome number by half, resulting in the formation of gametes. It consists of two main stages: meiosis I and meiosis II.

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

3. **Zygotene Stage**: In the zygotene stage, homologous chromosomes begin to pair up through a process called synapsis. This stage does not involve the separation of chromosomes due to repulsion.

4. **Pachytene Stage**: During the pachytene stage, crossing over occurs, where genetic material is exchanged between homologous chromosomes. While this is a critical stage for genetic variation, it does not involve the separation of chromosomes due to repulsion.

5. **Diplotene Stage**: The diplotene stage is characterized by the beginning of separation of homologous chromosomes. Here, the chromosomes start to move apart due to repulsion, but they are still connected at points called chiasmata, where crossing over has occurred.

6. **Diakinesis Stage**: In the diakinesis stage, the chromosomes are fully condensed and ready for metaphase, but the separation due to repulsion is no longer relevant as they are already positioned for separation.

### Conclusion:
The correct answer is the **Diplotene stage**, where homologous chromosomes separate due to repulsion but are still held together by chiasmata.

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