Distribution of gene frequencies and discrimination probabilities for 22 human blood genetic systems in four racial groups.

Gene frequencies were computed in four racial categories from 5956 blood donors from California, Hawaii, Mexico City, and Texas. Calculations were based on the phenotypic distribution of 22 blood genetic systems including 7 blood groups and 15 genetically controlled polymorphic proteins and enzymes. Matching probabilities for 20 systems were approximately 1 in 100 000 Asians, 1 in 200 000 blacks, 1 in 330 000 Mexicans, and 1 in 1 000 000 whites. The complementary discrimination probability, which measures the likelihood that two random individuals do not match, was, for practical purposes, unity. The combined new technology for blood grouping and electrophoresis using cellulose acetate membranes provides a powerful individualizing and discriminating tool for forensic science investigation.