Figure 2.

Duplication of chromosome IV is conditionally beneficial. (A) Replicates of a strain fully disomic for chromosome IV show significantly improved growth compared to euploid replicates when grown on agar plates supplemented with 7.5 mM hydrogen peroxide. However, when these strains are grown on agar plates with rich medium (B), euploid individuals show superior overall growth as compared to individuals disomic for chromosome IV. When both strains are exposed to 10 mM of hydrogen peroxide in liquid culture (C), euploid individuals also show higher growth than individuals disomic for chromosome IV. In (A) and (B), end-point colony pixel intensity measurements were generated using plate growth assays and image analysis in ImageJ. Mean and 95% confidence intervals are plotted. These measurements are based on four biological replicates per strain, which were each grown in three technical replicates (see Note S5 in File S1). In (C), individuals were exposed to hydrogen peroxide in liquid media for 3 d, after which the OD630 was measured for each culture. Measurements were again based on four biological and three technical replicates per strain (see Materials and Methods).