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Year 11 Meiosis helpp!!!

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Year 11 Meiosis helpp!!!

Postby JenL97 » Wed Oct 16, 2013 7:00 am

I have an exam coming up and I was looking through my notes and got confused. I have tried looking it up but cannot get the answer I want.

I know in meiosis that there is replication of the chromosomes and they line up in homologous pairs 'head to toe'. Cell division occurs and 2 daughter cells are produced both diploid cells. From these 2 daughter cells the chromatids are pulled apart and then cell divison occurs once more producing 4 daughter cells (haploid cells) all with different genetic information.

But I don't understand how the 4 daughter cells are all different as it seems 2 should be the same and the other 2 the same but different from the first pair. I have attached a picture of what I mean as I think it will be hard to understand what I am trying to ask.

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Re: Year 11 Meiosis helpp!!!

Postby ChrisHoStuart » Wed Oct 16, 2013 9:36 am

During the first part of meiosis (prophase 1) there can be recombination (crossover) of homologous chromosomes. This would show up on your diagram as being a little bit of red on one arm of the blue X, and a matching little bit of blue in the same place of the red X. That is a "cross over".

The final four cells will all be different. For each chromosome, you'd have one of the following:
  • red
  • blue
  • red with a bit of blue replaced
  • blue with a bit of ref replaced (a colour reversal of the previous case)

Have a look at the images by BioNinja, at his page Meiosis
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Postby JenL97 » Thu Oct 17, 2013 7:45 am

I think I understand what you mean now, that diagram was really helpful. Thank you so much!
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Postby Darby » Thu Oct 24, 2013 7:26 pm

Without crossing over, though, you are right - there are duplicate pairs.
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