Nucleotide sequence analyses of amplified GPIa cDNA derived from 2 Sit^a (+) individuals (A.I.1 and A.II.1; Fig 2). PCR product encompassing nucleotides 2304-2854 was subcloned into the plasmid vector pGEM-5Zf and sequenced on both strands using primers corresponding to the SP6 and T7 RNA polymerase promotor sequences. The base exchanges of the wild-type (WT) CA or CG to the mutant TG at positions 2531 and 2532 (arrows) result in a Thr₇₉₉ (ACA or ACG) → Met₇₉₉ (ATG) substitution.