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Genetic Couneling

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Genetic Couneling

Postby rxyz » Sun Jul 01, 2007 6:56 pm

I have a question, can you help?

In chromosome mapping, one map unit represents

not sure if the answer is: the distance between one gene and the next on a chromosome.



thanks in advanced :)
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Postby blcr11 » Mon Jul 02, 2007 7:55 am

I think it's a measure of the distance between two genes, they don't necessarily have to be adjacent genes.

I'm not a geneticist, so I could be wrong, but my understanding is that two genes separated by 1 map unit on the same chromosome segregate 1% of the time. At every meiosis, there is some chance that there will be a cross-over event between two genes such that they segregate. The physical separation between close genes makes it much less likely that they will segregate compared to genes at opposite ends of the same chromosome, or on separate chromosomes, so you can map the relative separation of genes based on segreation frequency. The physical "size" of the map unit in bp will be different for different sized chromosomes.
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Postby MrMistery » Mon Jul 02, 2007 8:42 pm

indeed. One centimorgan represents a 1% frequency of recombination. there is no connection between this and the physical distance between the genes. For example, because genes at the end of chromosomes tend to be transmitted together, genes appear to be "clustered" close to one another at the end of chromosomes.
However, linkage maps must not be underestimated. They do give the order of genes on a chromosome, and were the first step to sequencing the human genome.
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Postby khenwood » Tue Jul 03, 2007 4:54 pm

What does the question have to do with genetic counseling?

I'm going to assume this is just your play on words. :)
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Postby MrMistery » Tue Jul 03, 2007 6:29 pm

i think he meant that he needed someone to counseil him on genetics ;)
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Postby khenwood » Tue Jul 03, 2007 7:01 pm

Yep, that's what I figured.
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