FREQUENCY OF RECIPROCAL TRANSLOCATIONS AND DICENTRICS INDUCED IN HUMAN BLOOD-LYMPHOCYTES BY X-IRRADIATION AS DETERMINED BY FLUORESCENCE IN-SITU HYBRIDIZATION

This study was designed to test the scoring efficiency of reciprocal t ranslocations and dicentrics induced by X-irradiation in vitro using t he fluorescence in situ hybridization (FISH) technique. An excess was found in the frequencies of reciprocal translocations relative to thos e of dicentrics by measurement with FISH at the first cell division af ter irradiation (translocation:dicentric almost-equal-to 60:40). Howev er, when the same metaphases were also evaluated sequentially by a con ventional staining method, the ratio of about 50:50 was restored. This was due in part to misclassification of certain dicentrics as. recipr ocal translocations by the FISH technique.