Extra structurally abnormal chromosomes (ESACs)--presentation of 10 new cases

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.

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.

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.

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.