Mean dN/dS ratios for region groups.

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454 proteins contain poly-Q tracts of four or more glutamines in humans. However, this number excludes 41 human proteins without assigned homologs in either mouse or rat, which served as the references for estimating the dN/dS ratios. Additionally, the dN/dS ratios for some regions flanking the poly-Q tracts were not available by PAML estimation. The dN/dS ratios were calculated for a region including 33 amino acids on either side of the repeat and excluding the repeat.