FIG. 2.

The G44S mutation causes chromosome instability. (A) Mitotic chromosome stability tests. Representative pictures of colonies on YPD plates are shown at the top. The bar graph was prepared from three independent experiments with the standard error of the mean. Colonies with an at least 50% continuous red sector were counted as the first-division chromosome (Chr.) loss. Colonies that were totally red, as a result of chromosome loss prior to cell plating on YPD, were excluded. (B) G44S mutant cells lose viability faster after short benomyl exposure. Log-phase cells were treated with 60 μg/ml benomyl for the indicated time, washed, counted, and spread onto benomyl-free YPD plates. Percent viability was calculated by dividing the total number of colonies by the number of cells inoculated (counted microscopically) and was normalized to that of the T₀′ samples. Results are from at least three independent experiments. (C) Higher missegregation is associated with the G44S mutation. WT and G44S mutant cells with the TRP1 locus marked by GFP were treated with 30 μg/ml benomyl for 2 h, collected, and regrown in YPD medium containing α-factor for 2 h before fixation for microscopy. At least 200 unbudded cells with GFP dots were scored in four independent cell cultures of each strain. Green and red bars represent WT and G44S mutant cells, respectively. Error bars show standard deviations. Randomly selected images of two-dotted WT and G44S mutant cells (marked by white triangles) are shown on the right. w/o, without.