Why is crossing over so important actually?
Guys, our teacher said crossing over is super important but I don’t really get why. Okay, some genes swap places, but does it really matter that much? Can someone explain in simple words why we would die without it or something? Thank you!
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Crossing over is one of the main ways nature creates genetic variation. Full explanation with pictures is here if you want: phases of meiosis
During prophase I of meiosis, homologous chromosomes (mom’s and dad’s versions) come very close and actually break and swap matching pieces of DNA. This creates new combinations of alleles on the same chromosome. Without crossing over, each chromosome would always stay exactly as it was inherited from one parent. With crossing over, one chromosome can have some genes from mom and some from dad. This mixing, together with random alignment of homologues in metaphase I, makes sure that almost every gamete is genetically unique. That variety is very important for evolution – it gives natural selection more different options to work with. Without it, species would adapt much more slowly.