When synapsis is completed all along the chromosome, the'cell is said to have entered a stage.

Options

A. zygotene
B. pachytene
C. diplotene
D. diakinesis

Answer

To answer the question "When synapsis is completed all along the chromosome, the cell is said to have entered a stage," we need to understand the stages of meiosis and the process of synapsis. Here’s a step-by-step solution:

### Step-by-Step Solution:

1. **Understanding Synapsis**:
- Synapsis is the process where homologous chromosomes pair up during meiosis. This occurs during the prophase I of meiosis.

2. **Identifying Stages of Meiosis**:
- The prophase I of meiosis consists of several stages:
- Zygotene (zygotin)
- Pachytene (pachyten)
- Diplotene (diplotin)
- Diakinesis

3. **Zygotene Stage**:
- In the zygotene stage, homologous chromosomes begin to pair up, and this pairing process is known as synapsis. However, at this stage, synapsis is not yet complete.

4. **Pachytene Stage**:
- Following zygotene, the cell enters the pachytene stage. Here, the paired chromosomes (bivalents) become coiled and are more condensed. This stage is characterized by the completion of synapsis and the beginning of crossing over.

5. **Diplotene Stage**:
- After pachytene, the cell enters the diplotene stage. In this stage, the chromosomes begin to separate slightly, but the crossing over has already been completed. This indicates that synapsis is fully complete.

6. **Conclusion**:
- Therefore, when synapsis is completed all along the chromosome, the cell is said to have entered the **diplotene stage**.

### Final Answer:
The cell is said to have entered the **diplotene stage**.

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