FIGURE 4:

(A) Increased oxidative stress just during prometaphase reduces the temporal tolerance for prolonged prometaphase. Asynchronous cultures were treated with nocodazole plus KBrO₃ for 6 h and then both were washed out. Significantly fewer daughters born of mothers spending <1.5 h in prometaphase proliferated relative to the basic experiment (Figure 2A): p = 4.8 × 10^–5. For the daughters born of mothers spending >1.5 h in prometaphase, there was no significant increase in the proportion of cells that proliferated (p = 1.0). (B) Reduced oxygen level increases the temporal tolerance for prolonged prometaphase up to 6 h but does not abrogate the G1 arrest of daughter cells born of longer prometaphase durations. Asynchronous populations were treated with nocodazole for 10 h in medium equilibrated with 3% oxygen. After nocodazole washout, the daughter cells were followed at ambient oxygen levels.