Thick-thread stage occurred in :-

Options

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

Answer

To determine in which stage the thick-thread stage occurs, we need to analyze the options provided: Laptotene, Zygotene, Pachytene, and Diplotene.

### Step-by-Step Solution:

1. **Understanding the Stages of Meiosis**:
- Meiosis consists of several stages, and each stage has specific characteristics regarding chromosome behavior and structure.

2. **Identifying the Stages**:
- **Laptotene**: This is the first stage of prophase I in meiosis where chromosomes begin to condense but are not yet fully visible as thick threads.
- **Zygotene**: In this stage, homologous chromosomes begin to pair up, but the chromosomes are still not fully condensed into thick threads.
- **Pachytene**: This is the stage where chromosomes are fully condensed and appear as thick threads. It is also the stage where crossing over occurs between non-sister chromatids.
- **Diplotene**: In this stage, homologous chromosomes start to separate but remain connected at chiasmata. The chromosomes are still visible as thick structures, but they are not as condensed as in Pachytene.

3. **Conclusion**:
- The thick-thread stage is characterized by fully condensed chromosomes, which is observed in **Pachytene**. Therefore, the correct answer is option **3 (Pachytene)**.

### Final Answer:
The thick-thread stage occurs in **Pachytene**.