Chiasmata are the expressions of ……………….

Explanation

**Step-by-Step Solution:**

1. **Understanding Chiasmata**: Chiasmata are X-shaped structures that form during meiosis, specifically during the prophase I stage. They are crucial for genetic recombination.

2. **Homologous Chromosomes**: Chiasmata occur between homologous chromosomes, which are pairs of chromosomes (one from each parent) that are similar in shape, size, and genetic content.

3. **Sister and Non-Sister Chromatids**: In a homologous chromosome pair, there are sister chromatids (identical copies of a chromosome) and non-sister chromatids (chromatids from different homologous chromosomes).

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