http://ghr.nlm.nih.gov/gene/MC1R MCR1 mutation National Institutes of Health MC1R skin color National Institutes of Health skin color skin color NIH Genetics Home Reference skin color skin color National Institutes of Health National Institutes of Health National Institutes of Health http://ghr.nlm.nih.gov/gene/MC1R higher risk for melanomas http://ghr.nlm.nih.gov/gene/MC1R