Comparative genomic hybridization (CGH), which involves the simultaneous hybridization of differentially labeled total genomic DNA from test cells and reference normal cells to metaphase chromosomes, has been used extensively to screen tumor genomes for regions of DNA sequence copy number variation. Analysis of these hybridizations requires quantitative analysis of the ratio of intensities of the fluorescent hybridization signals as a function of position along the chromosomes, which basically serve as a convenient genetic map. The ratios need to be measured very accurately since changes of about ± 20% from the average for the genome indicate important genetic events. Widespread use of CGH over the past several years has identified numerous regions of the genome that may contain currently unknown cancer genes. For example, regions of increased copy number may indicate sites of oncogenes, while regions of copy number decrease relative to average for the genome may signify the presence of a tumor suppressor gene.
Measurement of DNA sequence copy number variation using comparative genomic hybridization to microarrays
