List the event which occurs during following stages:
1) Zygotene (ii) Pachytene (iii) Anaphase-I

Explanation

### Step-by-Step Solution

1. **Zygotene Stage:**
- During the Zygotene stage of prophase I in meiosis, homologous chromosomes begin to pair up. This process is known as **synapsis**. In this stage, the paternal and maternal chromosomes align closely together, forming pairs.

2. **Pachytene Stage:**
- In the Pachytene stage, which is also a sub-stage of prophase I, the non-sister chromatids of the homologous chromosomes undergo **crossing over**. This means that segments of genetic material are exchanged between the chromatids, leading to genetic variation. This exchange of chromatin segments is crucial for increasing genetic diversity.

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