Mapping the blond hair locus in Solomon Islanders. (A) A Manhattan plot and QQ-plot (inset) of the association scores comparing blond and dark haired individuals. The grey line indicates the genome-wide threshold for statistical significance. The QQ-plot shows the distribution of p-values before (black points; λ=1.02) and after (grey points; λ=1.00) removal of the 151 SNPs in the associated 9p23 region. (B) A regional plot of the GWA including the R93C allele, where the signal for the top SNP on the GWA array (blue diamond) and R93C (large red diamond) are indicated. The degree of redness of all SNP’s in the region indicates linkage disequilibrium with R93C. Also shown is recombination rate (navy line) at the signal peak in a window of ± 500 kb around the top GWA SNP. Positions, recombination rates and gene annotations are according to NCBI build 37 (hg 19).

PCA (A) and ADMIXTURE (B) plots demonstrating the genetic relationships between Solomon Islanders (blond and dark hair) genotyped in the present study and several other populations. In PC space, Solomon Islanders are found between New Guineans and Asians, which is consistent with their population history (7). Blond and dark-haired Solomon Islanders show no systematic differences in their ancestry suggesting that blond hair is unlikely to be due to gene flow from other populations (e.g. Europeans). (CEU = Europeans from HapMap; CHB = Han Chinese from HapMap; PNG = Papua New Guinea; MIC = Micronesians; POL = Polynesians; SI = Solomon Islanders).

Hair and skin pigmentation variants in TYRP1 (A) Top; a schema of the protein domains of TYRP1 (signal peptide (SI); epidermal growth factor (EGF), copper-binding and transmembrane (TM) domains) indicating variants in humans and other vertebrates that result in lightened skin and/or hair/coat (in brown) or albinism (in grey). Bottom; homology at the first 100 amino acids of TYRP1 in humans and other vertebrates. The location of the mouse brown^light mutation (R38C) and the Solomon Islands blond hair mutation (R93C) are given. (B) Boxplot showing the effect of the R93C genotypes on hair pigmentation in 921 Solomon Islanders.