Previously we have constructed 11 chromosome replacement lines between two closely related species, Saccharomyces cerevisiae (Sc) and Saccharomyces bayanus (Sb), so the contribution of individual chromosomes to hybrid incompatibility can be dissected (Lee et al, 2008). Despite that several genes involved in strong mitochondrial-nuclear incompatibilities have been identified, weak nuclear-nuclear incompatibiliies were widely observed in these lines but remained unexplored. Earlier studies indicated that transcriptome data can provide a sensitive way to detect hybrid dysfunctions (Ortiz-Barrientos et al, 2007 Mack et al, 2017 Swain Lenz et al, 2014). Thus, we evaluated the transcriptomic consequences due to the presence of foreign chromosomes in all 11 replacement lines. In addition to replacement lines, we also examined Sc, Sb, and Sc/Sb hybrid strains. Total RNA was isolated from cells grown at 23 degrees Celsius, a non-stressful temperature for both Sc and Sb, and examined using RNA sequencing.