Location and rapid analysis of the intragenic BamHI polymorphic site of the factor IX gene

We report the precise location and a polymerase chain reaction (PCR)-based method for the analysis of the intragenic BamHI polymorphism of the factor IX (FIX) gene. After screening DNA samples from the Brazilian Black population by a selective amplification of a segment of the FIX gene containing entire exon 2, intron 2, and exon 3 followed by digestion of PCR products with BamHI, we were able to identify individuals presenting the polymorphic BamHI site. By DNA sequencing of selected samples, the dimorphic base was located at nucleotide number 6575 (intron 2). The PCR method outlined here allows rapid and easy analysis of this polymorphism. Its application may be particularly useful for carrier detection and prenatal diagnosis of hemophilia B in the Black population, thus far the only one that has been shown to be polymorphic for this site. Because of its apparent restrictive pattern it may also be used in combination with other markers for estimates of racial admixture in mixed populations in which the Black population is present (as is the case for most countries in the American continent).