Meiosis - Somebody HELP! (1 Viewer)

[LuthienAdrianna]

Here's what I think happens in meiosis...

Say we have 4 chromosomes in the cell:

1) Chromosomes become visible (still 4)
2) Chromosomes duplicate (now 8)
3) Chromosomes pair up in homologous pairs [I've no idea what that means] (still 8)
4) Cell splits in two (two cells with 4)
5) Cells split again without duplication (four cells with 2 each, therefore haploid)

Something feels very wrong. My teacher says the first meiotic division is the important one because it does the haploid thing and the second division is just like mitosis, but according to the duplication thing, the first division is like mitosis and the second is the different one.

*argh*

 

[pLuvia]

3) Chromosomes pair up in homologous pairs [I've no idea what that means] (still 8)

This means the duplicated chromosomes pair up at the centre and after cytokinesis it splits. Cytokinesis occurs during one the phases I don't remember sorry

 

[Dr_Doom]

OMG I forget all this.. But this was peliminary right? Do we need to know Peliminary stuff for the HSC?

Josh

 

[pLuvia]

Well it's assumed knowledge, so it would help.

 

[Survivor39]

2) Chromosomes duplicate (now 8)
3) Chromosomes pair up in homologous pairs [I've no idea what that means] (still 8)

Just be careful of the terminology. It's not "8" chromosomes, rather it is 4 chromosomes, each with 2 attached chromatids (as a result of duplication).

Something feels very wrong. My teacher says the first meiotic division is the important one because it does the haploid thing and the second division is just like mitosis, but according to the duplication thing, the first division is like mitosis and the second is the different one.

well I just don't think you should use "mitosis" when explanation meiosis. The two resulting daughter cells after the first division are haploid, because they only have 1 copy of each of the chromosome (so therefore two in your case). Int he second division, the sister chromatids of the chromsome separate, 1 sister chromatid goes into 1 daughter cell, while the other goes into the other.

Let me illustrate
Parental cell containing
Chromosome 1 (C1) and Chromsome 2 (C2) Toal no. of chromosome = 4

Duplication of chromosomes:
Still 2 x C1 and 2 x C2 but each chromsome has 2 sister chromatids in cross-shaped.

Meiosis I:
2 daughter cells, each containing 1 C1 and 1 C2 (hence haploid)

Meiosis II:
4 daughter cells, each containing 1 C1 sister chromatid and 1 C2 chromatid (haploid).

I hope this makes sense.

 

[Survivor39]

My teacher says the first meiotic division is the important one because it does the haploid thing and the second division is just like mitosis...
*argh*

Both divisions are equally important. Non-disjunction occuring in any one of the steps will result in an abnormal gamate formation. e.g. extra chromosome or missing chromosome.