Background: The goal of the study was a search for effective methods of diagnosing additional marker chromosomes.
Material/Methods: Three cases of extra structurally abnormal chromosomes (ESACs) were diagnosed, the ESACs having been derived from chromosome 15 by cytogenetic techniques, the fluorescence in situ hybridisation (FISH) technique and the quantitative - polymerase chain reaction (Q-PCR). An application of a set of commercially available probes, specific for the 15q11.2-q12 regions (PWACR-Prader-Willi/Angelman Critical Region) allowed for a description of the breaking points.
Results: The presence of PWACR region was confirmed in one case and excluded in the other two. It was also attempted to apply the Q-PCR technique for a more accurate determination of the size of the region involved in chromosomal aberration, what would allow for a more reliable prognosing of the clinical outcome. In one of the patients, the breaking point was localized as distal to D15S144 locus, while it was proximal to D15S11 locus in the two remaining cases.
Conclusions: The obtained results demonstrate a possibility of using the Q-PCR method in diagnosing unbalanced chromosome aberrations

Keywords: supernumerary marker chromosomes, fish, Q-PCR