CHROMOSOME ABERRATION ANALYSIS IN ATOMIC-BOMB SURVIVORS AND THOROTRAST PATIENTS USING 2-COLOR AND 3-COLOR CHROMOSOME PAINTING OF CHROMOSOMAL SUBSETS

Chromosomal translocations in peripheral lymphocytes of three healthy Hiroshima atomic (A)-bomb survivors, as well as three Thorotrast patie nts and two nonirradiated age-matched control persons from the German Thorotrast study were studied by two- and three-colour fluorescence in situ hybridization (chromosome painting) with various combinations of whole chromosome composite probes, including chromosomes 1, 2, 3, 4, 6, 7, 8, 9 and 12. Translocation frequencies detected by chromosome pa inting in cells of the A-bomb survivors were compared with results obt ained by G-banding. A direct comparison was made, i.e. only those cell s with simple translocations or complex aberrations detected by G-band ing were taken into consideration which in principle could be detected also with the respective painting combination. The statistical analys is revealed no significant differences from a 1:1 relationship between the frequencies of aberrant cells obtained by both methods. The use o f genomic translocation frequencies estimated from subsets of chromoso mes for biological dosimetry is discussed in the light of evidence tha t chromosomes occupy distinct territories and are variably arranged in human lymphocyte nuclei. This territorial organization of interphase chromosomes implies that translocations will be restricted to chromati n located at the periphery of adjacent chromosome territories.