Fig. 3. The DNA damage checkpoint is activated in top3 mutants. (A) Fluorescence micrographs of DAPI-stained top3-134, top3-134 chk1, top3-134 cds1 and top3-134 rad1 cells grown at the permissive temperature of 26°C or after shift to 36°C for 9 hours. Bar, 10 µm. (B) At 3-hour intervals, samples from cultures of wild type (972), top3-134 and rad1 top3-134 cells incubated at the restrictive temperature of 36°C were taken to score the percentage of aberrant mitosis in each culture. (C). One thousand cells from B at the times indicated were plated onto YES plates to assess cell survival. Colonies were counted after 5 days growth at 26°C.