White TYMS polymorphisms and haplotype frequencies. The first and last exons of TYMS and the relative positions of the polymorphisms that were investigated are depicted. Thin lines indicate introns; boxes, exons (3′UTR is striped, 3R → 2R is dark fill, coding is light fill); dark triangles, polymorphisms; and light triangles, start and stop codons. Haplotype frequencies were determined using the Cocaphase program.