FIGURE 1:

(A) Times of individual daughter cell death after prolonged prometaphase. Points above the time line: for daughters born of 136 mothers spending 2–6 h in prometaphase, 69/136 (51%) died, and all but one died before the preparation became confluent (asterisk) due to the proliferation of a few cells starting at 72 h. Points below the time line: for daughters born of 40 mothers treated with nocodazole for 30 min, all daughters proliferated and by the end of the film runs 15/1776 (0.8%) of the progeny died, all after the culture became confluent (asterisk). Time line is hours after removal of nocodazole. (B) Two examples of the death of daughters born of mothers spending 2–6 h in prometaphase. First frames show blebbing activity and the second frames show terminal compaction of the same cells (arrows). Times are hh:mm after nocodazole removal. Phase contrast images, bar = 20 μm. (C) For daughters born of mothers held 2–6 h in prometaphase, evidence for activation of the apoptotic pathway at 18 h after nocodazole removal as detected with FITC-tagged annexin V (green contrast) for surface phosphatidylserine. Of the annexin V–positive cells, 14/68 (21%) show propidium iodide PI-positive nuclei (red contrast), indicating surface membrane permeability during later stage apoptosis (right-hand cell).  Phase contrast/fluorescence image, bar = 20 μm. (D) Senescence in some G1-arrested daughter cells born of mothers held 2–6 h in prometaphase. First and second frames show examples β-galactosidase positive cells still alive at 72 and 96 h after nocodazole removal. Third frame, none of the daughter cells born of mothers treated with nocodazole for 30 min are β-galactosidase positive at 72 h. Phase contrast images, bar = 20 μm.