What are the phases of meiosis where crossing over occur

What are the phases of meiosis where crossing over occur

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  1. each of the 46 original chromosomes splits into two daughter chromosomes, so there are two sets of 46 daughter chromosomes that end up in each cell. human cells have 46 chromosomes. each chromosome consists of a pair of identical chromatids attached together by a structure called a centromere.

  2. Prophase 1


    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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