Method
DNA from subject tissue and from normal control tissue (reference) are each labeled with different tags for later analysis by fluorescence. After mixing subject and reference DNA along with unlabeled human cot-1 DNA (placental DNA that is enriched for repetitive DNA sequences such as the Alu and Kpn family) to suppress repetitive DNA sequences, the mix is hybridized to normal metaphase chromosomes or, for array- or matrix-CGH, to a slide containing hundreds or thousands of defined DNA probes. Using epifluorescence microscopy and quantitative image analysis, regional differences in the fluorescence ratio of gains/losses vs. control DNA can be detected and used for identifying abnormal regions in the genome.
Currently, strategically placed oligonucleotides offer a resolution typically of 20–80 base pairs, as compared to the older BAC arrays offering resolution of 100kb.
Read more about this topic: Comparative Genomic Hybridization
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