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Genetics and Molecular Biology
On-line version ISSN 1678-4685
DIEGO, Yolanda de et al. Fragile X founder effect and distribution of CGG repeats among the mentally retarded population of Andalusia, South Spain. Genet. Mol. Biol. [online]. 2002, vol.25, n.1, pp. 01-06. ISSN 1678-4685. http://dx.doi.org/10.1590/S1415-47572002000100002.
Fragile X syndrome is the most common inherited form of mental retardation. We investigated the prevalence of the Fragile X syndrome in the population with mental retardation of unknown etiology in Andalusia, South Spain. We analyzed 322 unrelated patients (280 males and 42 females), and found a fragile X syndrome frequency of 6.5%. Among the non-fragile X chromosomes, the 29 CGG repeat was the most common allele. At the linked microsatellite DXS548 locus, we found a new allele which we called "allele 10" (17 CA). Similar to other south European populations, allele 2 (25 CA) at the DXS548 locus and the fragile X allele were in linkage disequilibrium supporting the idea of a common founder chromosome predisposing to the CGG expansion.
Keywords : mental retardation; fragile X syndrome; CGG repeats; genetic screening.