ThatOtherMegan
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Right, I've just hit a bit of a mental block here and just really confusing myself, so correct me if I'm wrong anywhere here. We know that meiosis is used to form gametes, (egg, sperm) so it forms haploid cells. However, what I'm getting confused about, it that if it is used to form gametes for fertilisation, then how does it also involve DNA from both paternal and maternal sides? How is there a mix of DNA to form a gamete? If an egg is being formed there is no mix of DNA? I know I'm probably just overlooking something simple so can someone please help? Sorry if I look absolutely stupid right now.
Thanks.


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KiwiMonkey96
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(Original post by ThatOtherMegan)
Right, I've just hit a bit of a mental block here and just really confusing myself, so correct me if I'm wrong anywhere here. We know that meiosis is used to form gametes, (egg, sperm) so it forms haploid cells. However, what I'm getting confused about, it that if it is used to form gametes for fertilisation, then how does it also involve DNA from both paternal and maternal sides? How is there a mix of DNA to form a gamete? If an egg is being formed there is no mix of DNA? I know I'm probably just overlooking something simple so can someone please help? Sorry if I look absolutely stupid right now.
Thanks.


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Meiosis does not involve DNA from both paternal and maternal sides, meiosis will make either an egg in females and a sperm in males and these gamates only contain the DNA from one parent, the DNA from the two come together during fertalisation to form the zygote, this will therefore contain both paternal and maternal DNA and not the actual gametes. I hope I have made some sense here, I do not find it easy to explain things.
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alicelovatt
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I think the mixing of DNA that you're getting confused with is the use of homologous pairs. One parent cell will contain two homologous chromosomes which genetically recombine by crossing over. Their chromatids twist around each other several times and then create tensions, so portions of the DNA breaks off and joins the homologous chromosome partner. This genetic material comes from only one parent.

Crossing over increases genetic variety as in Meiosis, four different cells can be produced.
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ThatOtherMegan
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Thanks for your replies, I understand it a lot better now! Anyway, my notes say that the independent segregation of homologous chromosomes causes variation (which I understand). But the thing is, my notes say that an each bivalent is made up of a maternal and paternal chromosome. Does this mean my notes are wrong?


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KiwiMonkey96
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(Original post by ThatOtherMegan)
Thanks for your replies, I understand it a lot better now! Anyway, my notes say that the independent segregation of homologous chromosomes causes variation (which I understand). But the thing is, my notes say that an each bivalent is made up of a maternal and paternal chromosome. Does this mean my notes are wrong?


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The gamates will only contain DNA from the organism it is from, This organism however contains half its DNA from ITS mother and the other other half from ITS father. When they line up in meiosis next to its homologous chromosome one of the chromosomes would have come from the organisms mother and one from its father, but the DNA is all from that organism, it is the fact that this organism got its DNA from 2 other individuals.
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