Following the number of chromosomes through Mitosis

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Following the number of chromosomes through Mitosis

Post by cctennisfan » Thu Oct 01, 2009 10:37 pm

Ok. At the end of MITOSIS, if a plant cell has 12 chromosomes, then shouldn't it have 6 chromosomes in the G2 phase of interphase? Those 12 chromosomes are actually in 2 separate nuclei at the end of mitosis, but not in different cells, which happens after the cell undergoes cytokinesis. So for this cell, there would be 6 single chromosomes in the G1 phase. Duplication occurs during the S stage. 6 chromosomes would still be present in the G2 phase, as chromatin connected by cohesins. Then, in prophase, the chromatin condenses into chromosomes, in this case 6. Go through Prometaphase and metaphase with no change in the number of chromosomes. Then, in anaphase, after the homologous chromosomes(1 chromosome=2 sister chromatids) are pulled apart by kinetechore microtubules, there would be a total of 12 chromosomes in the plant cell. this number would be preserved throughout Telophase, although the chromosomes would be incorporated into 2 separate nuclei, 6 per each. However, there is still one cell. Cytokinesis is not a part of mitosis, but is a part of the mitotic phase.

So here's a question:

1. If a plant cell has 12 chromosomes at the end of mitosis, how many chromosomes and chromatids does it have during the G2 phase?

Is all of my above information correct, and would the answers to this question be 6 and 12 respectively?

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Post by JackBean » Thu Oct 01, 2009 11:19 pm

Well, I think, that in the END of mitosis, are the 12 chromosomes in TWO nuclei in TWO cells, aren't they? :-P

Cis or trans? That's what matters.

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Re: Following the number of chromosomes through Mitosis

Post by SteveA » Thu Oct 01, 2009 11:31 pm

If the normal diploid chromosome number for this plant is 12, then prior to mitosis(during S phase of the cell cycle), each of the 12 strands of chromatin will be replicated forming 24 strands. These will condense into 12 pairs of sister chromatids when mitosis begins. The result will be that each daughter cell will have 12 chromosomes like the original parent cell.

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