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Fluorescent in situ hybridization with probes specific for a chromosomal subregion and chromosome-specific libraries (chromosome painting) are important new methods for assessing chromosome rearrangements. In this paper we present four patients with additional chromosomal material on chromosome 8p who have been studied using G-banding techniques, chromosome painting and FISH with cosmid probes specific for the region 8p23.1-->8pter. In all cases we found a partial inversion duplication of 8p along with a deletion of the region 8p23.1-->8pter.

Micro-FISH was used to elucidate the chromosomal origin of marker chromosomes in three patients. Ten copies of marker chromosomes were collected with microneedles from GTG banded metaphases, transferred to a collecting drop and amplified by means of DOP-PCR. The PCR products were labeled with biotin-14-dATP and used as FISH probes for hybridization to normal metaphase chromosomes and to metaphase chromosomes of the patients (reverse painting). With the generation of chromosome region-specific painting probes by PCR amplification of microdissected DNA and subsequent FISH it was possible to identify the marker chromosomes in all patients. One marker appeared to be derived from the centromere region of the X-chromosome and the proximal third of the long arm, one from the centromere region of chromosome 17 and one marker chromosome was identified as an isochromosome 18p.