Figure 2. Haplotypes of the human β₂-adrenergic receptor gene and identification of genetic risk profiles. This figure represents, from left to right, the specific alleles at each of 11 variable positions (relative to the translation initiation site) in this gene for a subgroup of nine individuals from the Bergen Blood Pressure Study.^55,56 1: Identical with reference sequence; 2: Different from reference sequence. The individual haplotypes are given by these specific combinations of 11 alleles as they occur throughout the gene. The three individuals at the top, who are genetically predisposed to essential hypertension, show potential risk haplotypes, which have in common a specific combination (“pattern”) of alleles at the first seven positions (marked in blue). This also demonstrates that the most frequently analyzed variant at position 46 (Arg>Gly) and the combination of the three in vitro functionally significant receptor mutations at positions -47, 46, and 79 are both insufficient to distinguish individuals at risk. Modified from reference 55: Hoehe MR, Timmermann B, Lehrach H. Haplotypes and the systematic analysis of genetic variation: disease genes, drug targets and pharmacogenomics [in German], Biospektrum. 2002:8:478-485. Copyright (c) 2002, Elsevier.