[Interest of studying subtelomeric abnormalities by in situ fluorescent hybridization to explore idiopathic mental retardation]

Nowadays, the genetic basis of mental retardation is a huge field of investigations. Genetic abnormalities frequently give rise to a mental retardation phenotype and are observed in 10 to 40% of known etiologies. New syndromes have identified [chromosome 1p, 22q, 3q29 and 9q34] but for 60% of patients there is no etiology because there is no characteristic phenotype. Many studies involve subtelomeric duplications and deletions in idiopathic mental retardation. The auteurs describe and discuss the interest and the limits of telomeric FISH [Chromoprobe Multiprobe T System] in exploring mental retardation

Interets et applications pratiques de la technique d'hybridation in situ en cytogenetique

The authors describe a recent technique of chromosome analysis introduced for the first time in a tunisian laboratory: the fluorescence in situ hybridization [FISH] which constitute a convergence point between cytogenetic and molecular biology. In situ hybridization [ISH] allow nucleics acids sequences localization on a chromosomal preparation by a molecular hybridation of a fluorescent or radioactive DNA target probe. The ISH was limited in the past to repeated sequences detection. Nowadays it is possible to detect single copies. This technique has many applications: cytogenetic diagnosis, genome mapping, cancerous and evolution mechanisms