Adaptive Evolution?
Somehow the article isn't available yet, but this is an advanced Epub on PubMed of a paper in Am J Hum Gen:
Adaptive Evolution of UGT2B17 Copy-Number Variation
Xue Y, Sun D, Daly A, Yang F, Zhou X, Zhao M, Huang N, Zerjal T, Lee C, Carter NP, Hurles ME, Tyler-Smith C.
Of course this sounds pretty interesting but, from the abstract alone, their title already seems quite lofty. The major beef is if you show polymorphism in both populations, but there is less variation in copy number in one, does that mean it's really adaptive? If you don't know what the function of the gene is, can you call something adaptive? It seems that they actually have a locus which has one of the many hallmarks of positive selection (or a sweep) but that's a long stretch from saying it's adaptive. Out of interest this comes from the same camp as the amylase adaption paper, which was generally well received but is not without it's own faults.
Adaptive Evolution of UGT2B17 Copy-Number Variation
Xue Y, Sun D, Daly A, Yang F, Zhou X, Zhao M, Huang N, Zerjal T, Lee C, Carter NP, Hurles ME, Tyler-Smith C.
The human UGT2B17 gene varies in copy number from zero to two per individual and also differs in mean number between populations from Africa, Europe, and East Asia. We show that such a high degree of geographical variation is unusual and investigate its evolutionary history. This required first reinterpreting the reference sequence in this region of the genome, which is misassembled from the two different alleles separated by an artifactual gap. A corrected assembly identifies the polymorphism as a 117 kb deletion arising by nonallelic homologous recombination between approximately 4.9 kb segmental duplications and allows the deletion breakpoint to be identified. We resequenced approximately 12 kb of DNA spanning the breakpoint in 91 humans from three HapMap and one extended HapMap populations and one chimpanzee. Diversity was unusually high and the time to the most recent common ancestor was estimated at approximately 2.4 or approximately 3.0 million years by two different methods, with evidence of balancing selection in Europe. In contrast, diversity was low in East Asia where a single haplotype predominated, suggesting positive selection for the deletion in this part of the world.
Of course this sounds pretty interesting but, from the abstract alone, their title already seems quite lofty. The major beef is if you show polymorphism in both populations, but there is less variation in copy number in one, does that mean it's really adaptive? If you don't know what the function of the gene is, can you call something adaptive? It seems that they actually have a locus which has one of the many hallmarks of positive selection (or a sweep) but that's a long stretch from saying it's adaptive. Out of interest this comes from the same camp as the amylase adaption paper, which was generally well received but is not without it's own faults.
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