Figure 4: (A) Three-SNP multiple linear regression (MLR) models for skin reflectance across populations (test sample set). The horizontal-axis depicts all 3654 combinations (i.e., 29-choose-3) of significant SNPs in a three-SNP MLR model. The vertical-axis is the R2 value for each model (black curve or three- SNP R2 curve) and also the SNP function value for each SNP curve. The R2 curve inflection (i=219) is indicated by a vertical black line. The SNP curves of the three highest frequency SNPs at i=219 are indicated by colors (rs16891982 (SLC45A2), red; rs1426654 (SLC24A5), green; rs2424984 (ASIP), brown). (B) Bar plot of the SNPs that were present in all models from i=1 to i=219.