Chromosome Y (chrY) from the mouse strain C57BL/6J (ChrYC57) was substituted for that of A/J mice (ChrYA). Cardiomyocytes from the resulting "chromosome substitution" C57BL/6J-chrYA strain were smaller than that of their C57BL/6J counterparts. In the opposite direction, when chrYA from A/J mice was substituted for that of chrYC57, cardiomyocytes from the resulting A/J-chrYC57 strain were larger than in their A/J counterparts. Genome-wide gene expression in cardiomyocytes was compared between these strains using the Illumina Mouse-ref8 BeadChip. The effects of strain and post-pubertal testosterone levels were tested by ANOVA of a factorial design with four experimental groups by genotype and castration treatment: ChrYA/intact, ChrYA/castrated, C57/intact, C57/castrated. Four animals per group were tested. For more information about the experimental samples, see Llamas et al., 2009. For information about the analysis of these data, see Verdugo et al. 2009.