Help me out...

[doc3232]

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Having trouble with meiosis:
Chiasmata??? Locations where crossing over may occur? Does crossing over have to occur or is it possible for it not to occur?
How do the two chromosomes attach? I read they are zipped all the way across...Are they attached at the centromeres?

I read somewhere that G2 does not occur before meiosis but G1 does...is that true?

 

[soopasteve]

Having trouble with meiosis:
Chiasmata??? Locations where crossing over may occur? Does crossing over have to occur or is it possible for it not to occur?
How do the two chromosomes attach? I read they are zipped all the way across...Are they attached at the centromeres?

I read somewhere that G2 does not occur before meiosis but G1 does...is that true?

to my understanding (and there may be some trivial exception) crossing over will always occur. the centromere is where sister chromatids attach. these sister pairs match up with their homologous partners through attachment at the chiasmata among non-sister chromatids (where crossover occurs). there is multiple crossover points not just the over simplified individual cross over on each side of the centromere that they show in textbook pictures.

 

[doc3232]

to my understanding (and there may be some trivial exception) crossing over will always occur. the centromere is where sister chromatids attach. these sister pairs match up with their homologous partners through attachment at the chiasmata among non-sister chromatids (where crossover occurs). there is multiple crossover points not just the over simplified individual cross over on each side of the centromere that they show in textbook pictures.

Thanks