Discrimination of heterogeneity with the alkaline Comet assay. The sensitivity of the comet assay for subpopulations was investigated. Therefore, samples treated with 0, 2, 4 or 8 Gy and cell mixtures (0 and 2 Gy, 2 and 4 Gy, 4 and 8 Gy) were analysed (200 leukocytes/sample of one donor). The respective histograms (a) and DNA damage in %Tail DNA with the corresponding standard deviations (b) were demonstrated. Two populations were detectable for mixture-samples from 0 to 4 Gy as indicated by a subdividing arrow.