Observed frequencies of NBS1 foci per cell nucleus in control cells, cells exposed to α and γ radiation alone, to α → γ and γ → α, as well as predicted values based on assumption of additivity.

The initial number of foci per nucleus is reported as the mean number of foci recorded in the 16th minute after start of irradiation (16th minute is the first minute of image series recorded for combined irradiations). The final number of foci per nucleus denotes the mean number of foci recorded in the 310th minute, which is the last minute of image acquisition of cells treatment with γ.