Adult, African Americans, Chromosomes, Human, Pair 6, Diabetes Mellitus, Type 2, Diabetes, Gestational, Female, Gene Frequency, HLA Antigens, HLA-A Antigens, HLA-B Antigens, Hemochromatosis Protein, Histocompatibility Antigens Class I, Humans, Iron, Iron Overload, Membrane Proteins, Mutation, Pregnancy