Recently, the gene structure for human F.VIII protein was clarified, and F.VIII DNA probes have been used for carrier detection and prenatal diagnosis ofhaemophilia A. In order to make sure that the phenomena are universal, we have analysed the RFLPs of F.VIII gene in 16 Japanese families with haemophilia A, including a female haemophiliac case, using an intragenic F.VIII DNA probe(F8A) and an extragenic(linked) DNA probe(Stl4-1).The probe F8A revealed two variant bands after digestion by Bel I. Of normal 60 X chromosomes (females) examined, about 85% bore the 879-bp fragment and 15%the 1165-bp fragment. Five of sixteen mothers of hemophiliacs, definite carriers, were found to be heterozygous for Bel I polymorphism. Since the relationship between Bel I alleles and hemophilia gene has been identified in the 5 families in which the mothers were heterozygous, we could diagnose the carrier status of two women whose brothers are hemophiliacs. Onthe other hand, we could identify that one "haemophilic woman" with less than 10% of F.VIII:C was a carrier status when we analysed the Bel I alleles in theother members of the family.The probe DNA(ST 14-1) revealed seven variant bands ranging from 5.5 kb to 3.4 kb after digestion by Taq I. In 6 out of 16 families, the RFLPs of ST 14 locus were informative for carrier detection.From these data, it was concluded that the Bel I polymorphism of F.VIII gene and the Taq I polymorphism of ST 14 locus were informative for carrier detection in 8 out of 16 families with haemophilia A
Feasibility of prenatal diagnosis and carrier detection in South African haemophilia A patients