Time course of DNA strand break repair of Jurkat cells in intervals of 5 min. Cells were X-irradiated on ice with 6.8 Gy (basal line). To measure DNA strand break repair, the damaged cells were incubated at 37°C for different time periods as indicated (grey columns). The black column represents level of SybrGreen fluorescence obtained in undamaged cells (P0 values). Error bars represent SDs from 3 replicates.