SURVEY OF THE FRAGILE-X SYNDROME AND THE FRAGILE-X E-SYNDROME IN A SPECIAL-EDUCATION NEEDS POPULATION

To begin to understand the population dynamics of the fragile X (FRAXA ) mutation and to learn more about the fragile X E (FRAXE) syndrome, w e have initiated a survey of children in special needs education progr ams in the public school system, With respect to the FRAXA syndrome, w e found approximately 1/1,000 full mutations among males, No large all eles at the FRAXE locus were observed among 462 individuals. The allel e distributions at the two loci among Caucasians and among African Ame ricans were examined as well as the level of heterozygosity. We found a significant difference in the FRAXA allele distribution among the tw o ethnic groups; the major difference was due to the lack of smaller a lleles among the African Americans. No difference was found for the FR AXE allele distribution among the two groups, The level of heterozygos ity was less than predicted by the allele distribution at both loci. T his is probably due to unidentified large alleles among females with a test result of a single band. Alternatively, this excess may indicate that the population is not at equilibrium. (C) 1996 Wiley-Liss, Inc.