CCDS levels of cross-hybridization. Cross-hybridizing CCDS IDs detected using the microarray platform. (a) Percentage of human CCDS IDs that are detected in each sample using the human microarray chip. (b) Percentage of mouse CCDS IDs that are detected in each sample using the mouse microarray chip. (c) CCDS IDs that cross-hybridize are identified by subtracting the CCDS IDs detected in a homogeneous tissue sample (the “A” set) from the union of the mixed tissue samples (B,C, &D).