Document Title: Gene Polymorphism and Human Pigmentation

To provide better customer service, NCJRS has made this Federally-funded grant final report available electronically in addition to traditional paper copies. Opinions or points of view expressed are those of the author(s) and do not necessarily reflect the official position or policies of the U.S. 1. Abstract The overall goal of this research project was to determine with a high degree of accuracy, the pigmentation phenotype (hair, eye and skin color) of an individual from a forensic DNA sample. Human pigmentation is programmed genetically. Genetic data suggested that most of the variation in human pigmentation is the result of the actions of only 3 or 4 genes. Candidate genes mediating pigment variation have been identified in previous animal and human genetic studies. These genes include those associated with oculocutaneous albinism (OCA) such as tyrosinase (OCA1), P transporter (OCA2), tyrosinase-related protein 1 (OCA3) and SLC45A2 (OCA4). Additional candidate genes include MC1R and ASIP (associated with mouse coat color and human hair color variation) and SLC24A5 (associated with population differences in pigmentation). In total, we examined 74 polymorphisms in candidate 23 genes. Our hypothesis was that polymorphisms within these specific pigmentation genes result in normal human pigment variation. We set out to correlate these polymorphisms with hair, skin and eye color. The application of this research to forensic science is the development of a finite and specific set human SNPs that can be used as a predictor of hair, eye and skin color. Our analyses proceeded in three phases: Phase 1 was the determination of the spectrum of polymorphism in these genes in a limited number of individuals of diverse ethnic origins and various pigmentation types. Phase 2 was the correlation of these SNPs with pigmentation types in a representative sample of individuals. Phase 3 was the testing of the models determined in Phase 2 and the adaptation of the analysis to forensic DNA samples. Phases 1 and 2 have been completed and Phase 3 is nearly complete. Using multiple linear regression (MLR) modeling, six SNPs in five genes were found to account for large proportions of pigmentation variation in hair, skin, and eyes in our across-population analyses: single polymorphisms in SLC45A2, SLC24A5, and OCA2 accounted for 77.3% of the variance in total amount of scalp-hair melanin; single polymorphisms in SLC45A2, SLC24A5, and MC1R accounted for 38.3% of the variance in the natural logarithm of the ratio of black-to-red melanin in scalp …