Gene levels of cross-alignment. Cross-aligning genes detected from the disjoint gene catalog using RNA-Seq. (a) Percentage of human genes that are detected in each sample when aligning to the human reference. (b) Percentage of mouse genes that are detected in each sample when aligning to the mouse reference. (c) genes that cross-align are identified by subtracting the genes detected in a homogeneous tissue sample (the “A” set) from the union of the mixed tissue samples (B,C, &D).