Single nucleotide polymorphisms of the factor IX gene for linkage analysis in the southern Chinese population.

Carrier detection and prenatal testing for haemophilia B in Oriental populations have been hampered by the lack of informative markers within the factor IX (FIX) gene. We detected a T/C nucleotide variation at nucleotide 32770 in the poly-A region of the FIX gene in the mother of a haemophilia B child. Analysis of 139 unrelated alleles revealed a heterozygosity rate of 0·193, 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 studied.