Fig. 1. S2 cells display cell-cycle arrest in response to HU or IR. S2 cells were treated with HU for 15 hours or treated with 150 Gy IR followed by 2 hours of recovery. Cells positively stained for PH3 were counted using flow cytometry. S2 cells showed a decrease in the proportion of mitotic cells when treated with HU (1.5%) or IR (1.6%) compared with untreated cells (4.3%). Error bars represent s.e.m. (n=13).