The fragile X syndrome: implications of molecular genetics for the clinical syndrome.
The fragile X syndrome of mental retardation is one of the most common genetic diseases. Characterization of the mutations involved has greatly improved our knowledge of the transmission of fragile X syndrome and new DNA-based diagnostics tools significantly outperform cytogenetic testing both for establishing the diagnosis and for determining carrier status. Fragile X mutations consist of an expansion of a CGG trinucleotide repeat localized in a gene (FMR-1) that is abnormally methylated in all affected individuals. They are classified as premutations (asymptomatic) and full mutations (associated with the disease). Several different DNA analysis protocols are used for fragile X genotyping but only a few have been tested on large samples of individuals. There are several clinical indications for direct DNA genotyping for fragile X including mental retardation, learning disability or hyperactivity in children with or without a family history of mental retardation, the establishment of carrier diagnosis in fragile X families and prenatal screening of children from carrier women.
Rousseau
F
F
Unité de Recherche en Génétique Humaine et Moléculaire, Centre de Recherche de l'Hôpital, St-François-d'Assie, Québec, Canda.
D002648:Child; D004252:DNA Mutational Analysis; D005260:Female; D005600:Fragile X Syndrome / Q000175:diagnosis / Q000235:genetics* / Q000517:prevention & control; D006580:Genetic Carrier Screening; D005838:Genotype; D006801:Humans; D008297:Male; D008403:Mass Screening; D008967:Molecular Biology; D009838:Oligodeoxyribonucleotides / Q000235:genetics; D010375:Pedigree; D010641:Phenotype; D011247:Pregnancy; D011296:Prenatal Diagnosis; D012091:Repetitive Sequences, Nucleic Acid
D009838:Oligodeoxyribonucleotides