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| Author | Francene Cauchi |
| Abstract | Mental retardation is present in about 3% of the total population. In more than half of the cases the cause is unknown and these are therefore labelled as idiopathic. The telomeric ends of human chromosomes are gene rich regions, having the highest gene density in the entire genome. Rearrangements in the subtelomeric part of chromosomes are believed to be an important cause of idiopathic mental retardation. Many studies have reported on the use of specific fluorescence in situ hybridization (FISH) probes to aid in the detection of these rearrangements. The incidence of subtelomeric chromosomal rearrangements in idiopathic mentally retarded individuals is between 2 to 13%. The primary objective of this study was to optimise a laboratory protocol for specific FISH probes. Once this protocol was established it was applied for the detection of subtelomeric aberrations in idiopathic mentally retarded individuals. In this study, 32 idiopathic mentally retarded patients of varying severity and contrasting dysmorphic features were investigated for subtelomeric rearrangements by the use of specific FISH probes. Rearrangements were detected in 3 individuals. These were an unbalanced translocation between 7pter and 9pter. a subtelomeric 18p deletion and a subtelomeric 21q deletion. The prevalence of clinically significant subtelomeric rearrangements by subtelomeric FISH in this study was thus 9.4%, indicating that these rearrangements are an important cause of idiopathic mental retardation and dysmorphology. |
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| Key words | Medical Laboratory Science, Thesis, FISH, Subtelomeric Chromosomal Rearrangements, Idiopathic Mental Retardation |