5 polymorphism, rs16969968, a non-synonymous coding SNP in exon 4 of CHRNA5, causes an aspartic acid-to-asparagine substitution that alters the function of the nicotine receptor. The findings for the alpha-5 receptor were strengthened by a recent study by Berretini et al.[15], in which a highly correlated CHRNA5/CHRNA3 haplotype (cluster of linked genes) was shown to be associated strongly (P < 10−6) with smoking behavior (cigarettes smoked per day).
