Lesions that impede replication forks cause increased progeny lethality, apoptosis, and chromosomal fragmentation in rfs-1 mutants. (A–D) Percentage progeny survival of N2 (Wt), brc-1(tm1145), and rfs-1(ok1372) animals treated with the indicated doses of ionizing radiation (IR; (A)), cisplatin (CDDP; (B)), nitrogen mustard (HN2; (C)), and CPT (D). Error bars indicate standard error of the mean (s.e.m.) from at least 24 adult worms over two independent experiments. (E) Number of apoptotic corpses scored by DIC microscopy in animals of the indicated genotype before (untreated), or 24 h post-treatment with 75 Gy IR, 180 μM CDDP, or 150 μM HN2. Error bars indicate s.e.m. from at least 20 adult animals. (F) Percentage of examined chromosomes at the diakinesis stage of meiosis I with abnormalities. Young adult animals were dissected and fixed before (untreated) or 24 h post-treatment with 75 Gy IR or 180 μM CDDP, and DNA was observed by counterstaining with DAPI. At least 50 oocyte nuclei at diakinesis were scored for chromosomal abnormalities (e.g., alteration in bivalent number or fragmentation) per strain for each condition. Representative images are shown in Supplementary Figure 5.