Figure i. Genomic expression measured in unstressed wild-type cells is highly reproducible. Poly-adenylated RNA isolated from wild-type cells grown on different days in different batches of YPD media were differentially labeled with Cy3-dUTP and Cy5-dUTP and subjected to microarray analysis. Approximately 25 transcripts showed differential expression in these experiments greater than 2-fold, and no transcripts were affected greater than 2.5-fold. Linear regression analysis was performed on the normalized signal intensities measured for the Cy3-labeled sample (x-axis) versus the Cy5-labeled sample (y-axis). The linear fit is represented by the equation shown in the upper left of the plot, showing that the growth conditions and microarray measurements performed in this study were highly reproducible. The genomic expression response to MMS was highly similar in mec1 cells and dun1 cells (see Figure iii), further demonstrating the reproducibility of the microarray measurements.