Phenylketonuria causes a severe cognitive disability due to the inability to metabolize phenylalanine. It is an autosomal recessive disorder. About one in 12,000 newborns in Massachusetts are afflicted with the disease, skewed higher than the general US population due to more Irish-Americans. Assuming the gene is in Hardy-Weinberg equilibrium, the frequency of the carriers (heterozygotes) in Massachusetts would be calculated to be...