Why does crossing over occur at prophase 1 and not metaphase 1?

[Jay20155555]

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Why does crossing over occur at prophase 1 and not metaphase 1?

 

[cdp1210]

I believe the synaptonemal complex that temporarily forms between homologous chromosomes to allow for crossing over is only present in prophase I. As the complex is not present in metaphase I (or any of the other phases) recombination can only occur during prophase I.

 

[510586]

Also a good way to think about it imo is that in prophase, the stuff is lining up like next to each other and crossing over happens while in metaphase, they are all aligned top to bottom to split later on.