[Recombination between the fragile site Xq27 and the gene for coagulation factor IX]

Using the Taq I restriction polymorphism of a factor IX probe, we analysed the segregation of this gene and that of the fragile site Xq27. The ancestor of this family was a healthy carrier male. Of twelve informative meioses, at least four recombinations were detected. The hypothesis of a particular instability of the distal part the long arm of the X chromosome is reconsidered.