CHROMOSOME-SPECIFIC COMPARATIVE GENOME HYBRIDIZATION FOR DETERMINING THE ORIGIN OF INTRACHROMOSOMAL DUPLICATIONS

Chromosome specific comparative genome hybridisation (CGH) is a novel approach for the detection of cytogenetic abnormalities. It combines f low sorting of chromosomes, degenerate oligonucleotide primed (DOP)-PC R and a modified comparative genome hybridisation (CGH) technique to d efine the site and extent of intrachromosomal duplications. Chromosome specific paint probes for aberrant chromosomes and their normal homol ogues from four subjects with unbalanced duplications within chromosom es 2p11-15, 3q25-26, 5q34-qter, and 12q23-24.2 were made. They were th en cohybridised on normal metaphase spreads and the ratio of their rel ative intensities of hybridisation analysed. The results were compared to those of similar experiments where regular CGH was performed on th e same four patients. We provide evidence that this method can detect duplications and deficiencies which might be missed by conventional CG H, as the ratio of hybridisation of abnormal/normal DNA is 2:1 rather than 3:2. It is the method of choice where mosaicism is present or whe re only one of several homologous chromosomes is duplicated. Furthermo re, it suggests that DOP-PCR amplifies all or most of the euchromatic regions of the genome equally.