||We have identified a novel xylose-utilization phenotype controlled by a single gene, and we sought to characterize how both the presence and absence of xylose in the presence or absence of the trait affected the S. cerevisiae transcriptional program over time. To do so, we measured global steady state mRNA levels on three pairs of sister spores from a Simi White strain that was backcrossed twice to S288c. Each pair of spores was from an independent tetrad, and contained one xylose utilizing ("positive", GSY2465, 2466, 2469) and one xylose non-utilizing spore ("negative", GSY2464, 2467, 2470). We grew each of the six spores in the presence or absence of xylose for 72 hours with samples taken every 8 hours. We then assayed relative RNA abundance versus a pooled reference, containing equimolar amounts of each sample, using Agilent yeast catalog arrays.