A factor IX gene probe: its use in carrier detection, antenatal diagnosis and characterisation of the molecular basis for hemophilia B.

Of hemophilia B carriers, 67% were shown to have informative restriction fragment length polymorphisms (Taq I or Xmn I) associated with the factor IX gene. Analysis of DNA for these polymorphisms can enable the detection of the hemophilia B carrier state in females and of hemophilia B in the male fetus in the first trimester. Extensive mapping of the factor IX gene in one hemophiliac who developed antibodies to factor IX failed to detect structural abnormalities in his gene. A non-deletional basis for hemophilia B is proposed in this instance.