Temporal responses of p53 in normal cells and tumor cells. Time series plot of p53 (solid blue line) and repair process (dotted red line) at various initial damage levels (A-C: normal cells, k5 = 1, D: tumor cells, k5 = 3). A) IR = 0.3 Gy. B) IR = 3 Gy. C) IR = 20 Gy. D) IR = 3 Gy. The dynamics of p53 shows digital or undamped oscillations.