Possible founder effects for FRAXE alleles

To determine if FRAXE alleles may have haplotype associations with nearby m icrosatellites, we analyzed 149 unrelated control Caucasian X chromosomes f or FRAXE GCC alleles along with five nearby microsatellites, The microsatel lites included three that are new; GT25, CA4, and CA5 located similar to 24 , similar to 48, and similar to 50 kb proximal to the FRAXE GCC repeat, and two that were identified previously: DXS8091 and DXS1691, located similar to 90 and similar to 5 kb distal, No significant correlations between haplo types for the proximal microsatellites were found, Significant correlations of FRAXE GCC repeats and distal microsatellite allele sizes, DXS8091 (r = 0.24) and DXS1691 (r = -0.40), were found. One haplotype, 18-19 of DXS8091- DXS1691, was present on 57% of chromosomes with greater than or equal to 22 FRAXE repeats but present on only 10% with <22 repeats. We conclude that t his distal haplotype association likely reflects a FRAXE allele founder eff ect. The lack of association or founder effects seen for the three newly id entified proximal markers, located within 50 kb of FRAXE, GCC, may reflect an unusually high rate of mutation for these microsatellites or a higher ra te of recombination in the proximal region. (C) 1999 Wiley-Liss, Inc.