Pooling expertise in genetic testing: an innovative approach to NHS cytogenetics

Karyotyping, the staining of metaphase chromosomes to produce distinctive banding patterns, has historically been an important technology for cytogeneticists to view gross genetic differences. However, the requirement to grow cells in culture, and the ability to only detect aberrations >5 Mb, are both limitations to this methodology. Fluorescence in situ hybridisation (FISH) techniques, which use fluorescently labelled DNA probes to identify sequences of interest on the chromosome, have the advantage that they can provide higher resolution and can detect microdeletions, as well as balanced and unbalanced translocation events. Although FISH can be performed on uncultured cells, the number of probes that can be used simultaneously on the DNA is limited.
       Microarrays are now a preferred choice for a variety of reasons. First, the higher resolution permits an unparalleled view of the genome and a better insight into the mechanisms behind certain genetic diseases. Thanks to microarray technology, researchers have a clearer idea of the role copy number variation (CNV) plays in the pathogenesis of a number of diseases. Copy number variation is defined as the duplication/deletion of large segments of DNA, including one or more genes. They have been implicated in a number of genetic disorders including constitutional diseases and syndromes with aspects of developmental delay (eg 17q21.31 microdeletion syndrome).

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