[physicshelpme]

I'm so confused on what this actually is. I'm fine with mitosis but in the cgp book the meiosis part is laid out very badly and unclearly. Firstly it says that meiosis creates 4 seperate gametes with half the number of chromosomes so that when it becomes a zygote it will have the full number, but in the explanation it says that 'some of the fathers chromosomes and some of the mothers chromosomes go into each new cell' but doesn't that contradict what it has said before as it hasn't actually fused with another gamete yet? Or am I overthinking this?

[kooks78]

Hey! Actually my exam tom is on genetics
And u my friend are overthinking this. Ill enclose a pic of meisos process
Hope it helps


This was posted from The Student Room's iPhone/iPad

[ummm]

(Original post by physicshelpme)
I'm so confused on what this actually is. I'm fine with mitosis but in the cgp book the meiosis part is laid out very badly and unclearly. Firstly it says that meiosis creates 4 seperate gametes with half the number of chromosomes so that when it becomes a zygote it will have the full number, but in the explanation it says that 'some of the fathers chromosomes and some of the mothers chromosomes go into each new cell' but doesn't that contradict what it has said before as it hasn't actually fused with another gamete yet? Or am I overthinking this?

All of your body cells contain a mixture of maternal and paternal chromosomes - you inherited 23 from your mother, and 23 from your father, giving each body cell 46.

In meiosis, the body cells in the gonads (the testes and ovaries) divide to produce gametes containing half the amount of DNA (so 23 chromosomes each). First of all, the chromosomes are doubled, so the cells contain 92 chromosomes. Then two divisions take place. During the first, two cells are produced containing 46 chromosomes each. These then divide again, having the number of chromosomes again, so that there are only 23 in each cell. These are the gametes. These gametes combine at the moment of fertilisation to form a cell with the full number of chromosomes, called the zygote. This divides by mitosis to develop into an organism.

I think it is just trying to tell you that because your body cells contain a mixture of maternal and paternal chromosomes, your gametes will also contain a mixture of maternal and paternal chromosomes. Simple as that.

[physicshelpme]

so basically, it is just mitosis twice?

[ummm]

(Original post by physicshelpme)
so basically, it is just mitosis twice?

Yeah, two divisions.

92 chromosomes --> 46 chromosomes --> 23 chromosomes.