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Quelle: Edelmann Hirschhorn 2009 Seite(n): 157, Zeilen: right col.: 10 ff. |
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| In the 1990s the introduction of molecular cytogenetic techniques into the clinical laboratory setting represented a major advance in the ability to detect known syndromes and identify chromosomal rearrangements of unknown origin. Fluorescence in situ hybridization (FISH), which is the annealing of fluorescently labelled locus-specific probes to their complimentary sequences in the genome, allowed the detection of specific microdeletion syndromes (Fig. 2).5 There are currently a number of commercially available FISH probes for the most common disorders, and this method is still predominantly used when the clinical phenotype is suggestive of a particular disorder. Several other FISH-based methods, including spectral karyotyping (SKY), multicolour FISH (m-FISH),5 and comparative genomic hybridization (CGH) have proven extremely useful in the identification of unknown chromosomal material. SKY and m-FISH rely mainly on the principal of differentially labelling each chromosome using a unique combination of fluorochromes and are especially beneficial for identifying the origin and content of supernumerary marker chromosomes (SMCs) and complex chromosome rearrangements (CCRs) that involve more than two chromosomes. CGH was originally introduced for the cytogenetic analysis of solid tumors, which can be difficult to culture, and involves the differential labeling of DNA from a test sample and a reference sample (Fig. 3).5 The fluorescently labelled reactions are combined and hybridized to metaphase spreads from chromosomally normal individuals. Gains and losses of the genome in the test sample relative to the control sample are represented as ratios that are quantified from digital image analysis. This method allows the investigation of the whole genome and is very useful for determining the origin of unknown genetic material, such as SMCs and other unbalanced rearrangements.5 However, CGH does not detect balanced rearrangements, and the resolution is on the order of 5–10Mb, and consequently many genomic disorders cannot be detected.3
3 Edelmann L, Hirschhorn K: Clinical utility of array CGH for the detection of chromosomal imbalances associated with mental retardation and multiple congenital anomalies. Ann N Y Acad Sci 2009; 1151: 157-166. 5 Trask BJ: Fluorescence in situ hybridization: applications in cytogenetics and gene mapping. Trends Genet 1991; 7: 149-154. |
In the 1990s the introduction of molecular cytogenetic techniques into the clinical laboratory setting represented a major advance in the ability to detect known syndromes and identify chromosomal rearrangements of unknown origin. Fluorescence in situ hybridization (FISH), which is the annealing of fluorescently labeled locus-specific probes to their complimentary sequences in the genome, allowed for the detection of specific microdeletion syndromes.6 There are currently a number of commercially available FISH probes for the most common disorders, and this method is still predominantly used when the clinical phenotype is suggestive of a particular disorder. Several other FISH-based methods, including spectral karyotyping (SKY), multicolor FISH (m-FISH),7,8 and comparative genomic hybridization (CGH), have proven extremely useful in the identification of unknown chromosomal material. SKY and m-FISH rely mainly on the principal of differentially labeling each chromosome using a unique combination of fluorochromes and are especially beneficial for identifying the origin and content of supernumerary marker chromosomes (SMCs) and complex chromosome rearrangements (CCRs) that involve more than two chromosomes. CGH was originally introduced for the cytogenetic analysis of solid tumors, which can be difficult to culture, and involves the differential labeling of DNA from a test sample and a reference sample.9 The fluorescently labeled reactions are combined and hybridized to metaphase spreads from chromosomally normal individuals. Gains and losses of the genome in the test sample relative to the control sample are represented as ratios that are quantified from digital image analysis. This method allows for investigation of the whole genome and is very useful for determining the origin of unknown genetic material, such as SMCs and other unbalanced rearrangements.10 However, CGH does not detect balanced rearrangements, and the resolution is on the order of 5–10Mb, and consequently many genomic disorders cannot be detected.
6. Trask, B.J. 1991. Fluorescence in situ hybridization: Applications in cytogenetics and gene mapping. Trends Genet. 7: 149–154. 7. Speicher,M.R., S. Gwyn Ballard&D.C.Ward. 1996. Karyotyping human chromosomes by combinatorial multi-fluor FISH. Nat. Genet. 12: 368–375. 8. Speicher, M.R. & N.P. Carter. 2005. The new cytogenetics: Blurring the boundaries with molecular biology. Nat. Rev. Genet. 6: 782–792. 9. Kallioniemi, O.P. et al. 1993. Comparative genomic hybridization: A rapid new method for detecting and mapping DNA amplification in tumors. Semin. Cancer Biol. 4: 41–46 |
Source is given in Fn. 3. |
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