Comparing the organization of the human and mouse PPARδ genes. A. The human PPARδ gene (85 kb) located on chr6, B. The mouse ortologue gene (70 kb) located on chr17. The overall difference in length can be accounted for by the 63 kb versus 50 kb separating exon 2 and the first coding exon (4 or 3) in human and mouse genes, respectively. The relative positions of exons along the genes are given, specifying exons that are conserved between species (white boxes) and species-specific exons (black boxes). Arrows indicate the position of the initiation codon ATG and the stop codon TAA, respectively, with the intervening coding exons.