Full Duffy DNA typing. (A) Strategy of the PCR-RFLP for the detection of the C286T substitution specific of FY*X allele. Primers Fy7 and Fy57 were designed to amplify a 251-bp FYfragment encompassing the single base substitution identified between the Fy(a−b+) and Fy(a−b^weak) clones and that was correlated with an allele-specific Aci I restriction site. Nucleotide numbers are as in Fig 3 and do not take into account the intronic sequence of the FY gene. (B) DNA from donors with the indicated Duffy phenotype was used as templates in PCR-RFLP assays. Ten donors with each control phenotypes were analyzed and typical results are shown. The detection of the FY*A-, FY*B-, andFY*Fy-associated polymorphisms (G125A and C-46T, respectively) were based on Ban I and Sty I RFLP, as previously described, with some modifications for FY*Fy typing (see Materials and Methods). The TAR sample gave the same RFLP pattern as SEV and BE.T. The tree of the BE. family is shown to follow the inheritance of the FY*X mutation and to demonstrate that the presence at the heterozygous state of the silent allele FY*Fyin BE. father accounts for the apparent exclusion of paternity (BE.T being Fy^a-negative, with both parents being Fy^a-positive).