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meiosis help??? important

Hi,
From what little I've understood, meiosis is used to form gametes, so sperm and egg cells, so that they have half the number of chromosomes from diploid cells. And since genetic variation occurs in meiosis, this stems from the use of maternal and paternal chromosomes crossing over, right?

But surely the maternal and paternal chromosomes haven't 'met' since egg and sperm cells are being made in different bodies? There's something I'm missing and if someone could clear this up for me I'd be so grateful! Thanks
Original post by sophiespratt
Hi,
From what little I've understood, meiosis is used to form gametes, so sperm and egg cells, so that they have half the number of chromosomes from diploid cells. And since genetic variation occurs in meiosis, this stems from the use of maternal and paternal chromosomes crossing over, right?

But surely the maternal and paternal chromosomes haven't 'met' since egg and sperm cells are being made in different bodies? There's something I'm missing and if someone could clear this up for me I'd be so grateful! Thanks


Maternal and Paternal means the person's father and mother and not the parents of the unborn/non existent zygote
Mother and Father originally create it (especially in females)
Sperm meets egg.
They do it.
Genetic information crosses over. (Delves into A level)
They line up, then pulled by the spindle fibres
It happens again.
Gametes - random mix of mother and father
Original post by ThunderBeard
Mother and Father originally create it (especially in females)
Sperm meets egg.
They do it.
Genetic information crosses over. (Delves into A level)
They line up, then pulled by the spindle fibres
It happens again.
Gametes - random mix of mother and father


Don't listen to him/her.

That is completely wrong at all levels.
Original post by CuriosityYay
Don't listen to him/her.

That is completely wrong at all levels.

How? Then how is it? I’m unsure now
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Avatar for emlouu
emlouu
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Original post by sophiespratt
Hi,
From what little I've understood, meiosis is used to form gametes, so sperm and egg cells, so that they have half the number of chromosomes from diploid cells. And since genetic variation occurs in meiosis, this stems from the use of maternal and paternal chromosomes crossing over, right?

But surely the maternal and paternal chromosomes haven't 'met' since egg and sperm cells are being made in different bodies? There's something I'm missing and if someone could clear this up for me I'd be so grateful! Thanks

Each one particular person has 50% maternal chromosomes (DNA) and 50% paternal chromosomes (DNA) in every single body cell, this DNA is from that person's own parents. The maternal and paternal DNA is already there in the body cell from which the gametes are produced. Fertilisation is a separate process and occurs after gametes have been produced by meiosis.
Thank you for your help!
Original post by emlouu
Each one particular person has 50% maternal chromosomes (DNA) and 50% paternal chromosomes (DNA) in every single body cell, this DNA is from that person's own parents. The maternal and paternal DNA is already there in the body cell from which the gametes are produced. Fertilisation is a separate process and occurs after gametes have been produced by meiosis.

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