In the given options, which one is a characteristic features of the zygotene stage to prophase - 1 observed in meiosis ?

Options

A. Chromomeres
B. Crossing over
C. Terminalisation of chiasmata
D. Synaptonemal complex

Answer

To solve the question regarding the characteristic features of the zygotene stage in prophase 1 of meiosis, we can follow these steps:

### 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 and meiosis II. Prophase 1 of meiosis is further divided into five stages: leptotene, zygotene, pachytene, diplotene, and diakinesis.

2. **Identify the Zygotene Stage**: The zygotene stage is the second stage of prophase 1. During this stage, homologous chromosomes begin to pair up in a process called synapsis.

3. **Key Features of Zygotene**: The most significant feature of the zygotene stage is the formation of the synaptonemal complex. This complex is a protein structure that forms between homologous chromosomes, facilitating their pairing.

4. **Synaptonemal Complex**: The synaptonemal complex consists of a central element and lateral elements that connect homologous chromosomes. It is crucial for the proper alignment and pairing of homologous chromosomes, which is essential for the next stages of meiosis.

5. **Eliminate Other Options**:
- Chromomeres are visible in later stages and are not specific to zygotene.
- Crossing over occurs in the pachytene stage, not in zygotene.
- Terminalization is observed in the later stages of prophase 1, particularly in diakinesis.

6. **Conclusion**: Based on the understanding of the zygotene stage and the elimination of other options, the characteristic feature of the zygotene stage in prophase 1 of meiosis is the formation of the synaptonemal complex.

### Final Answer:
The correct option is the **synaptonemal complex**.

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