Single nucleotide polymorphisms of the factor IX gene for linkage analysisin the southern Chinese population

Carrier detection and prenatal testing for haemophilia B in Oriental popula tions have been hampered by the lack of informative markers within the fact or IX (FIX) gene. We detected a T/C nucleotide variation at nucleotide 3277 0 in the poly-A region of the FIX gene in the mother of a haemophilia B chi ld. Analysis of 139 unrelated alleles revealed a heterozygosity rate of 0.1 93, thus offering an additional marker for linkage analysis. Together with two other polymorphic sites (5' MseI and 3' HhaI) found in Chinese and Thai populations, these polymorphisms were useful in 66% of the families studie d.