Entry into apoptosis irrespective of cell cycle position. (A) Cell cycle of BAF3 cells prelabeled for 2 hours with BrdU, irradiated with 4 Gy, and incubated in the absence or presence of IL-3. After the times shown, cells were fixed and labeled with PI and anti-BrdU as described in the Materials and Methods. Squares marked G1 and Apo/G2 represent the gates set to sort populations that were then photographed using fluorescent microscopy. (B) BAF3 cell cycle analysis after the treatments indicated below each panel.