In situ hybridization centromeric probes - Molecular cytogenetics - Microdeletation syndromes

Microdeletion syndromes are defined as a group of syndromes characterized by microscopic and submicroscopic deletions of contiguous genes from parts of chromosomes, each of which may contribute independently to the phenotype. Genetic changes in the microdeletions are often not visible at standard karyotype resolution or even at high resolution (2-5 Mb) in contrast to chromosome deletion syndromes and require molecular cytogenetic techniques such as fluorescence in situ hybridization (FISH). Fluorescence in situ hybridization has now become the standard diagnostic approach for known common microdeletions. Phenotype is the result of haplo deficiency of specific genes in the critical interval. Well-described clinical syndromes for which the involvement of several deleterious genes has been established or is strongly suspected include velocardiofacial syndrome (22q11 microdeletion), Williams syndrome (7q11 microdeletion), neurofibromatosis type 1 (17q11 microdeletion), Smith-Magenis syndrome (17p microdeletion) and 8p microdeletion syndrome. Correlations between chromosomal rearrangements and clinical manifestations or genotype/phenotype correlations can provide essential information for the discovery of developmental causes and effects.