DOSE-RESPONSE CURVE FOR CHROMOSOME TRANSLOCATIONS MEASURED IN HUMAN-LYMPHOCYTES EXPOSED TO CO-60 GAMMA-RAYS

Chromosome painting was employed to measure frequencies of reciprocal translocations in human lymphocytes induced by Co-60 gamma rays, with emphasis on low doses. Translocations and dicentrics were distinguishe d by use of a pan-centromeric probe. A total of 41,151 metaphases were analyzed at doses below 0.2 Gy. The linear ''take-off'' slope of the linear-quadratic dose-response curve for translocations, i.e., the alp ha coefficient, was measured to be 0.023 +/- 0.005 translocations per cell per Gy. This alpha coefficient is more precise than previously me asured. Because the alpha coefficient is the dominant contributor to t he translocation frequency induced by low-level exposures, the results presented here will substantially reduce uncertainties in biodosimetr y estimates obtained for stable translocations.