Distribution of radiation induced lesions in human chromosomes and dose-effect relation analysed with G-banding

Human female lymphocytes were exposed to X-rays in vitro at 7 different doses between 40-280 R. In 830 metaphases chromosome analyses were carried out with either conventional staining or G-banding, respectively. 486 breakpoints are non-randomly distributed between chromosomes and chromosome arms. An excess of lesions was present in chromosomes 1 and 5 or in 1p. 85% of the lesions were located in G-negative bands (pale G-bands). 29% of all lesions appeared in either the last terminal pale band (21%) or in the centromere region (8%). With regard to an application of G-banding for a biological dose-estimation, the dose-response relations of dic and ace were analysed. Although G-banding enables detailed analysis of the whole karyotype it cannot be recommended for cytogenetic routine analyses in medical radioprotection monitoring, without suitable automated scoring techniques. Dose estimations based on the frequency of dic and carried out with conventional staining cannot be essentially improved at present with banding. Nevertheless, by banding criteria for a correct evaluation of other aberration types, e.g. ace, can be provided. This is a prerequisite for the calculation of representative dose-effect curves.