Schematic comparative structure of the DARC cDNAs isolated from whole blood of Fy(a−b+) and Fy(a−b^weak) donors. The full-length major isoform (spliced) of the FY transcripts was isolated by RT-PCR. The nucleotide sequences of Fy(a−b+) and Fy(a−b^weak) cDNA clones were identical, except for the C286T substitution (+1 taken as the erythroid cap site) resulting in the Arg89Cys polymorphism on the DARC protein. G was found at nucleotide position 319 in all clones from four unrelated Fy(a−b^weak) donors, whereas G or A, resulting in Ala100Thr amino acid change, could be found in the FY*B allele from Fy(a+b+) and Fy(a-b+) donors. The nucleotide residue found at the Fy^a/Fy^b-associated polymorphic position (G125A) is indicated.