Phenotype–genotype correlation. Average changes in diastolic blood pressure on treatment with metoprolol. Persons with two copies of the most common allele (S49R389) showed significant decreases in blood pressure. Those with one variant allele (GR or SG) showed more modest decreases, and those with two variant alleles (GR/SG) showed no decrease.
[Data from J. A. Johnson et al., Clin. Pharmacol. Ther. 74:44–52, 2003.]