Genotype versus phenotype: human pigmentation.

The natural range of hair and skin colour is a continuous spectrum, controlled by multiple genes in a complex fashion. Many of these genes are as yet unknown, but several key pigmentation genes have been characterised, in particular the melanocortin 1 receptor gene (MC1R). Here, the function and known mutations of MC1R and other human pigmentation genes including ASIP, MATP, SLC24A5, TYR, TYRP1 and OCA2 are outlined, and a forensic test based on MC1R SNPs presented. The forensic utility of this and potential future genetic tests for phenotypic traits are discussed, in the light of the extensive debate on the ethics of predicting phenotypic traits from crime scene samples.