Identification of a new CA dinucleotide repeat in the human factor VIII gene

We describe the identification of a new CA dinucleotide repeat marker for t he diagnosis of haemophilia A carriers. The marker (CA-6) is present in int ron 6 as a single copy 5 kb upstream of exon 7. Of 195 and 118 X chromosome s from normal individuals and haemophilia A patients, respectively, we obse rved three alleles of CA-6 with 12-14 repetitions [(CA)(12-14)]. The freque ncies were 0.5% and 0% for (CA)(12), 99% and 95.8% for (CA)(13), and 0.5% a nd 4.2% for (CA)(14) in normals and patients respectively, We conclude that the low polymorphism of the CA-6 marker renders it less useful for the dia gnosis of Chinese haemophilia A carriers.