Radiation-induced chromosome aberrations analysed by two-colour fluorescence <em>in situ</em> hybridization with composite whole chromosome-specific DNA probes and a pancentromeric DNA probe.

Fluorescence in situ hybridization with composite whole chromosome-specific DNA probes for human chromosomes 1, 4 and 12 and a degenerate &alpha;satellite pancentromeric DNA probe labelled with digoxigenin was used to measure symmetrical translocations and dicentrics induced in vitro by 137Cs &gamma;rays (0-6.0 Gy) in peripheral lymphocytes. Despite subtracting our mean background translocation frequency of 0.0016 per cell (11 411 cells scored from 11 individuals) from induced frequencies, about 1.3-1.8-fold more translocations were found than dicentrics at a given dose. Translocation frequencies determined only in stable cells agree well with total translocation frequencies determined also in cells containing additional unstable chromosomal changes. The linear quadratic calibration curve generated for total stable translocations is based on approx. 17 000 cells. The suitability of this curve for biological dosimetry of human radiation exposure can now be evaluated in comparison with dose estimates based on a conventional dicentric dose-response curve