View source for Meiosis

==== Diplotene ====
It is initiated by desynapsis of homologous chromosomes. Disruption of synaptonemal complexes occurs in it. Bivalents remain connected in one or more places ('''chiasmata)'''.

* '''homologous chromosomes''' begin to separate, the synaptonemal complex breaks down (desynapse)
* in the places of '''crossing over''', the chromosomes remain connected to each other, these places are so-called '''chiasmata'''
* the distribution of chiasmata is not regular, they can occur '''anywhere''' on the chromosome
* however, there are places where crossing over occurs more often - '''recombination "hotspots"''' and, conversely, places with a low probability of occurrence (e.g. pericentromeric region)
* it is also possible to observe the phenomenon of '''chiasmat interference''', i.e. reducing the likelihood of a chiasm forming near the appearance of another (the mechanism is still unclear)
* in humans we usually find '''1-3 chiasmata''' on each homologous pair (according to the size of the chromosomes), in total we find '''40-50 chiasmata''' in one cell
* to ensure '''correct segregation''' in the further course of the first meiotic division, at least '''one chiasma''' occurs even on the smallest chromosome
* four chromatids are already clearly recognizable in '''each bivalent,''' the entire structure of a homologous pair of chromosomes is called a '''tetrad'''