The authors thank Cristina Cartoni, Sébastien Lamy, and Charles Thomas at the Center of Phenogenomics (CPG, EPFL) for help in establishing and phenotyping the BXD mice, Jesse Ingels who genotyped the congenic AHR line. We thank the Molecular Resource Center of Excellence at The University of Tennessee Health Science Center processing all microarrays. Thanks to Ian Duncan for supplying the mutant ss D. melanogaster lines. Discussions with Prof. Stephan Morgenthaler (EPFL) are also acknowledged.