Average log signal intensity for all 3,456 clones. Shown here are average global log signal intensities values for same-species and cross-species hybridization. Results are separated according to the respective species of the clone in order to compare same-species versus cross-species hybridization. Probe species are indicated inside each bar. Bt; Bos taurus, Mm; Mus musculus, Xl; Xenopus laevis.