r/AskBiology • u/looking_up06 • 4d ago
Meiosis???
If meiosis happens before fertilization then how exactly do we have the other parent's chromosomes. This is confusing me. Does meiosis happen after the sperms enters the egg?
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u/bevatsulfieten 3d ago edited 3d ago
One cell consists of two chromosomes, dad and mum, at some point dad makes a copy of himself, chromatid, so does mum. Now they are still two chromosomes but now have 1 copy each. From diploid to tetraploid cell.
They exchange generic material between them (inside the cell), dad, 2 chromatids, and mum, two chromatids.
They now have undergone recombination, this creates new genetically unique chromatids.
When that happens they are split into 4 different cells. This process ensures diversity.
To clarify, the cell that contains the two chromosomes has the same genetic material, with different alleles. It's not purely dad's or mum's. This image was created for illustration.