Fig. 2. Chromosome segregation defects in top3-134 cells require passage through S-phase. G1-arrested wild type (top3⁺) and top3-134 cells were released into nitrogen-rich medium to restart the cell cycle at the permissive temperature of 26°C for 5 hours before shifting to the restrictive temperature of 36°C. Cells harvested at hourly intervals were processed for flow cytometry (A), and assessed for mitotic index (B) and aberrant mitosis (C) as in Fig. 1.