Fragile X Syndrome: Genetic Backgrouds

• Author(s): Loureiro, Joana ; Marques, Isabel ; Oliveira, Bárbara ; Amorim, António ; Santos, Rosário ; Jorge, Paula
• Date: 2010
• Persistent ID: http://hdl.handle.net/10400.18/697
• Origin: Repositório Científico do Instituto Nacional de Saúde
• Subject(s): FRAXA; Doenças Genéticas
• Document Type: Conference Object
• Language: English

Description

Fragile X Syndrome (FXS) is the most frequent hereditary form of mental retardation, caused by an expansion of polymorphic [CGG] repeats in the 5’UTR region of the FMR1 gene; the molecular mechanism of this expansion is, however, still unknown. Based on [CGG] triplet number, three allele classes can be distinguished: normal sized-alleles (5-50 repeats); pre-mutation alleles (50-200 repeats) and the full mutation where alleles have an expansion of over 200 CGG repeats. Previous studies using Short Tandem Repeat (STR) haplotypes of mutant chromosomes in diverse populations revealed founder effects based on linkage disequilibrium between CGG repeats and flanking molecular markers.