Fig. 6. Pulsed-field gel electrophoresis analysis of chromosomes from the top3-134 mutant. (A-C) Equal numbers of cells were prepared in agarose gel plugs from exponentially growing cultures of wild type (top3⁺) or top3-134 cells (four independent isolates) at the permissive temperature of 26°C (A), after nitrogen starvation to arrest cells in G1 (B), or following HU block (3 hours at 36°C) and release (C). Cells were harvested at the time of HU addition (C) and at hourly intervals after removal of HU for up to 3 hours. Arrowheads indicate the aberrant chromosome III band seen in top3-134 samples. (D) Flow cytometric analysis of the DNA content of ethanol-fixed, Sytox Green-stained samples from the experiment shown in C. (E) Samples from C taken at the times indicated were used to score the percentages of aberrant mitosis in each culture.