Alu repeats in the human factor IX gene: the rate of polymorphism is not substantially elevated.

Previous data suggested an elevated rate of polymorphism in Alu sequences. Direct genomic sequencing was performed on five Alu repeats in the factor IX gene in at least 20 unrelated males of European and Asian descent (40 kb total). In these Alu sequences, the estimated rate of polymorphism in Caucasians (HE = 7.1 x 10(-4); HN = 4.5 x 10(-4) is similar to previously examined nonrepetitive sequences in the factor IX gene, and about twofold lower than previous estimates of the average rate of polymorphism for the X-chromosome which utilized random genomic clones to detect RFLPs. The aggregate data on the rate of polymorphism in Alu sequences suggest that mutations due to gene conversions at these sites are infrequent.