The 81st Annual Meeting of the American Association of Physical Anthropologists (2012)

Tabula incondita: Mixed phylogeographic signals found within a megabase of chromosome 9


Department of Anthropology, University of Louisville

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It is well known that geographic distributions of many alleles are clinal. These phylogeographic patterns likely represent the spread of variability under a model of a wave of diffusion or document successive founder events into virgin territory. Genetic hitch-hiking predicts that linked variability gives concordant patterns contingent on the impact of recombination events and the influence of signals propagated by nearby genes. Here, a phylogeographic analysis of one megabase from chromosome 9 reveals multiple interspersed and conflicting signals.

This study uses Stanford CEPH-HGDP SNP data of 675 unrelated individuals from 36 Eurasian populations to explore whether estimates of anisotropy are concordant within one megabase from chromosome 9 (q33.3-34.11; 129,500,000 - 130,500,000). The set of genotype data for this region includes 169 SNPs that are on average 5,924 bases apart. This stretch of DNA has a moderately high recombination rate, multiple LD blocks when analyzed for major regional populations, and many genes. Analysis of anisotropy using angular correlation reveals significant correlations for 122 SNPs; 61 SNPs indicate a general East-West cline and 61 SNPs a general North-South cline. The signals of anisotropy of the different SNPs, however, are effectively interleaved often with adjacent SNPs giving opposite and significant signals. This is in contrast to previous work done on a single large gene on chromosome 1 that showed concordant signals in adjacent SNPs within the same linkage blocks. In the present case, gene density, the influence of selection, and recombinational history appear to have well-mixed the region.

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