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Name: Frank
Status: Educator
Grade:  Other
Location: Outside U.S.
Country: Canada
Date: October 2008

Regarding human evolution: A chromosomal fusion event occured in our (human) evolutionary history that brought our number down to 23 pairs (vs 24 in other apes). How would this type of mutation (I believe its termed a Robertsonian translocation) get passed on?

I don't believe it is an example of Robertsonian translocation because that is when two acrocentric chromosomes break apart at the centromeres and two of the nonhomologous arms fuse together. My understanding of the fusion that occurred in primates to make the human diploid number was when two whole chromosomes fused. The p arms of both are fused. The evidence for this is that there is telomeric DNA internally, as if the ends of two chromsomes fused at their tips. There are also two centromeres, although one of them has accumulated enough mutations that it doesn't serve as a second centromere any more.

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I must be missing something here. A fused chromosome would get passed on the same way any other chromosome that confers a selective advantage on the organism would.

Ron Baker, Ph.D.

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