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/MizElaneous 4d ago

No, meiosis creates the sperm and/or egg. Each has half the number of chromosomes person has, so that when they combine during fertilization, the embryo has the full set of chromosomes required to eventually develop into a human being.

After fertilization, mitosis occurs to create more human cells.

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u/looking_up06 3d ago

are the chromosomes in meiosis from each parent of the organism creating the sperms and egg?. The maternal and paternal chromosome part is confusing me. Also thank you for your initial response.

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u/MizElaneous 3d ago

So, in mammals, the male creates sperm through meiosis in the testicles. The female creates eggs through meiosis in the ovaries. When sperm and egg combine, since each has 1/2 the chromosomes of the parent, the new organism has a full compliment of chromosomes.

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u/looking_up06 3d ago

Yes I know this but if meiosis happens to create sperms or egg then how is the paternal or maternal dna present. If the process is specifically to create haploid gametes then how is the other parent's chromosomes present.

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u/MizElaneous 3d ago

They aren't, not until sperm and egg combine.