Abstract

Background: The goal of the presented studies as a retrospective reliability assessment of classical banding cytogenetic studies and of prognosing epicrises in a group of 14 cases, affected with additional marker chromosomes.
Material/Methods: Having collected the study material from peripheral blood, by means of trophoblast biopsy or amniocentesis, cytogenetic preparations were obtained, allowing for pre- or postnatal evaluation of the karyotype. A panel of auxiliary cytogenetic techniques accompanied the routine CTG protocol.
Results: In a group of 6875 persons with recommendations to pre- or postnatal cytogenetic diagnostics, 14 (0.2 %) cases of ESACs were diagnosed. In 5 cases of DA/DAPI(+) inv dup (15) as observed. A presence of polymorphic interstitial RHG(+) band was found within the marker chromosome. The measured size of that band allowed associating it with either the presence or the absence of pathological signs. In 9 cases of ESACs, DA/DAPI(-), the application of banding techniques (NOR and CBG) allowed to discover bisatellite heterochromatic ESACs in 6 cases (2 non-mosaic and 4 mosaic). In three other mosaic and non-satellite cases of ESACs, a 'genetic inactivity' of the marker chromosome was observed in one case, while a 'genetic activity' was ascertained in two cases. The 'activity' of marker chromosomes was studied by means of replication banding techniques.
Conclusions: At the time of the outburst of molecular techniques, still up-to-date is the use of classical banding techniques and of the replication techniques, allowing DNA replication kinetics studies at the level of single band.

Keywords: supernumerary marker chromosomes, phenotypic prognosis