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distinguishing between meiosis 2 and mitosis

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distinguishing between meiosis 2 and mitosis

Postby year12biologyfml » Wed Nov 04, 2009 9:42 am

hello, i was doing some revision for my exam and i came across this multiple choice question. i'm not sure about their cos i thought it would be D cos i didn't think there was any way to distinguish between the 2nd stage of meiosis and mitosis?

here is the question (word for word, i found their wording a little tricky)

If you found a cell from a diploid organism in the process of division as in the diagram below you could best describe this as

Image
plz excuse the poor drawing

J mitosis only
K the first division of meiosis
L the second stage of meiosis
M either mitosis or meiosis

their answer was L, but I thought it would be M because i don't believe you can distinguish between the 2nd stage of meiosis and mitosis?
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Postby kolean » Fri Nov 06, 2009 2:12 pm

Was that the exact drawing they gave you? Was there any color on the chromosomes?
Because this looks really like meiosis 1 division, cause to me they look like they are duplex chromosomes going to their seperate MTOCs. Which would mean that they were tetrads at the beginning. The chromosomes also look very similar, and thus a paternal one and a maternal one. Interesting......
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Postby jyaron » Wed Nov 11, 2009 2:16 am

I don't believe there is enough information to determine whether one is paternal or maternal, as kolean described.

Based upon the image, the answer would be L, the second stage of meiosis. The first division of meiosis would divide a tetrad into a diad.. you would see a traditional "><" chromosome going to each of the daughter cells in the first meiosis division.

The second meiosis division yields haploid daughter cells, which is what is displayed in the image above.

Mitosis, on the other hand, always yields diploid daughter cells in diploid organisms (no taking into consideration aneuploidy that may occur in cancer cells, etc.). As such, an image of mitosis would show the traditional "><" chromosome image being pulled by each microtubule stand to each side of the dividing cell.

In summary:

Mitosis:
  • Diploid original cell ("><")
  • Duplication of genome in S phase of the cell cycle (">< ><"; for each chromosome)
  • During division each daughter cell receives one "><"
Meiosis I:
  • Diploid original cell (germ cell) ("><")
  • First genome duplication (">< ><")
  • Crossing over/Recombination occurs
  • First Meiotic division, each daughter receives "><"
Meiosis II:
  • First daughter cell generation ("><")
  • No genome duplication.
  • Second meiotic division, each haploid daughter receives (">", or "<")

Is it clear now?
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