DHFR polymorphisms and derived haplotypes. (A) Promoter polymorphisms with the frequency of minor alleles. (B) Haplotypes arbitrarily named from *1 to *5 derived from 13 promoter polymorphisms with minor allele frequency higher than 1%. tagSNPs that are sufficient to infer all 5 haplotypes are given in bold. Pairwise estimates of linkage disequilibrium are given the bottom panel (▩ indicates r² = 1; □ indicates r² < 1). (C) Haplotypes derived from 3 tag promoter SNPs and the 19-bp indel polymorphism. The frequency of controls is given next to the haplotypes.