Changes in the cell cycle phase distribution of the mutant p53 cell line MEF 10(1) following 10 Gy γ-irradiation. Cells were pulse-labeled for 30 min with 10 μM BrdUrd in complete medium at 37°C at the indicated times post-irradiation. Bivariate BrdUrd-PI flow cytometric analysis was performed as described in Materials and Methods. 20000 cells were analyzed at each time point. Closed circles, percentage of cells in G1 phase of the cell cycle; open triangles, percentage of cells in S phase of the cell cycle; closed squares, percentage of cells in G2 phase of the cell cycle.