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Genetics as it applies to evolution, molecular biology, and medical aspects.

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seeking answer

Postby pengliu » Wed Sep 14, 2005 10:41 pm

flowering plant with a somatic chromosome number of 34, 16 bivalents at meiosis 1, one of which involve chromosomes very much longer than any of the others.
what does it say?
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Postby MrMistery » Thu Sep 15, 2005 8:07 pm

Do you mean you don't understand what it says? Well, at meiosis the chromosome number is half:16, not counting 2 sex cromosomes. Also, as you probably know, not all cromosoms have the same size. The first pair in human is bigger than all the others. By the way, does that go for all organisms?
Anyway, hope this helps
Regards,
Andrew
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Postby pengliu » Fri Sep 16, 2005 4:19 am

Yeah, I know. but plants are different. I found some materials and wrote below:
Plant nuclear genomes exhibit extensive structural variation in size, chromosome number, number and arrangement of genes, and number of genome copies per nucleus. Commonly, 17 bivalents will be found at meiosis I if a flowering plant has 34 somatic chromosomes in a cell. From the analysis of the genome sequence of Arabidopsis thaliana, some evidence show there are segmentally duplicated regions in the Arabidopsis genome, and Gaut & Doebley (1997) suggested that Arabidopsis, like maize, had a tetraploid ancestor. So we can suppose that if the new species has divergence from an ancestral autotetraploid form (we noticed the fact 4 NORs at interphase) and 2 bivalent chromosomes at metaphase I of meiosis appear to be associated in groups of two because of their significant similarity, obviously we would only see 16 bivalents. From above, the genome of flowering plant has many dispersedly and segmentally duplicated regions and could be an autotetraploid form in plant evolution. On the contrary, someone who denied the theory said the segmental duplication events happened separately instead of tetraploid formation and stabilization (nature 2000).

MrMistery wrote:Do you mean you don't understand what it says? Well, at meiosis the chromosome number is half:16, not counting 2 sex cromosomes. Also, as you probably know, not all cromosoms have the same size. The first pair in human is bigger than all the others. By the way, does that go for all organisms?
Anyway, hope this helps
Regards,
Andrew
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