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Originally posted by pseudobug:
Do you happen to know if the gene arrangement in the vicinity of the fusion junction in the human chromosome is similar to that of chimp chromosome 24?
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Well the G banding patterns are the same: From what I gather, this is a way to "fingerprint" a chromosome. From <a href="http://www.waisman.wisc.edu/cytogenetics/procedures/G-Banding/G-banding.html" target="_blank">this site:</a>
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GTL-Banding or just "G-Banding" stands for Giemsa/Trypsin/Leishman banding. This method of staining devised by Dr. Giemsa uses typsin to partially digest the proteins holding the chromosomes together (histones). This lets the chromosome relax, letting the Leishman stain bind to the exposed DNA.
The resulting bands are specific to each chromosome and the order and size of the band lets cytogeneticists distinguish and compare homologous pairs of chromosomes.
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So what do the G banding patterns look like when you compare human and chimp? From the site I linked to in my first post:
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Except for differences in non genetic heterochromatin, chromosomes 6, 13, 19, 21, 22, and X have identical banding patterns in all four species. Chromosomes 3, 11, 14, 15, 18, 20, and Y look the same in three of the four species (those three being gorilla, chimps, and humans), and chromosomes 1, 2p, 2q, 5, 7 - 10, 12, and 16 are alike in two species. Chromosomes 4 and 17 are different among all 4 species.
Most of the chromosomal differences among the four species involve inversions - localities on the chromosome that have been inverted, or swapped end for end. This is a relatively common occurrence among many species, and has been documented in humans (Ref. 8 ).
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So the genes are either in the same order, or in reverse order, if there was an inversion.
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Don Lindsay provides a diagram of the chromosome 5 inversion between chimpanzees and humans scanned from ref. 1. Note how all of the bands between the two chromosomes will line up perfectly if you flip the middle piece of either of the two chromosomes between the p14.I and q14.I marks. The similarity of the marks will include a match for position, number, and intensity (depth of staining). Similar rearrangements to this can explain all of the approximately 1000 non-heterochromatic bands observed among each of the four species for these three properties (band position, number, and intensity).
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Although they didn't go into depth on the genes, it appears that the large markers do line up. I'm sure the genes do too.
scigirl
07-24-2002, 07:08 PM
