What are the phases of meiosis where crossing over occur

Prophase 1

Explanation:

Prophase I :It can be divided into five stages:

1)Leplotene: In this stage, chromosome becomes visible and shorten as a single structure.

2)Zygotene: Homologous / sister chromosome pair up. This process is known as synapse. Synapse is the process of attachment of homologous /sister chromosome. One pair comes from the male parent while the other comes from the female parent.

3)Pachytene: Bivalents shorten.

4)Diplotene:Point of attachment of non-sister chromatids. The two chromosomes are seen to be joined at several points along their length. These points are known as Chiasmata.(Chiasmata, a cross). The paternal gene A, B, C may swap for the maternal gene a, b, c for instance, leading to a new gene combination in the resulting chromatids. This is referred to as *CROSSING OVER*.

5)Diakenesis: Homologous centromere move apart.

So, crossing over occurs in *Prophase 1.

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