FIGURE 5.

Competition assay between wild-type cells and cells lacking snR191. The amount of wild-type cells (LMA5–1D strain) relative to cells lacking snR191 (LMA247 strain) during the course of cultures is measured by the relative quantification of PCR products arising from LMA5–1D (wild type) cells (PCR product generated by the GB241 and GB243 oligonucleotides) or LMA247 (ΔsnR191 mutant) cells (PCR product generated by the GB241 and GB242 oligonucleotides) (see Materials and Methods). (A) PCR samples from standard (top) or competition experiments (bottom) were loaded on an 8% acrylamide-urea gel. The figure shows PhosporImager images of the gels. For calibration, standard reference values were generated by quantifying, with a PhosphorImager, the relative amount of the PCR products generated from known mixed fractions of wild-type and ΔsnR191 yeast cells. The evolution of the fraction of wild-type cells during the competition experiment was measured by quantification of the PCR products and normalization using the values determined in the standard experiment. (B) The averaged quantifications of wild-type over mutant cells (% of wild-type cells), averaged from six independent cultures, are plotted to the number of generations. Standard deviations are shown.