Genome-Wide Association Studies of Quantitatively Measured Skin, Hair, and Eye Pigmentation in Four European Populations
Figure 2
Comparison of measured and self-reported hair and eye color.
(A) The boxplots of hair pigmentation (M index) binned by self-reported hair color show that there is a good correspondence between categorical hair color and the M index. On average, individuals with red hair color (n = 6) have lower M indices than blond individuals (n = 58). Individuals reporting brown (n = 252) or black (n = 11) hair color have the highest M indices. (B) Similarly for eye pigmentation, the C’ score corresponds well to the self-reported eye color. Individuals reporting blue (n = 123), green (n = 97), hazel (n = 14), and brown (n = 212) eye color have increasing average C’ scores. We note that one individual has a discrepant self-reported color vs. C’ score. This individual self-reported light brown eye color but the C’ score is indicative of most likely blue eye color. This individual was part of the replication cohort and removing the sample from the association study produces similar p-values, only slightly less significant for the OCA2/HERC2 SNPs. Each box in the plot is drawn with a width proportional to the square root of the sample size.