Fig. 2.
Comparison of mouse and human ORs. An unrooted phylogenetic tree showing protein sequence relationships among representatives of all mouse (green) and human (red) OR subfamilies. One member of each subfamily was used (435 sequences) in addition to 25 ORs with known ligands (black). Mouse and human ORs are interspersed throughout the tree, indicating that the OR repertoires of the two species are similar. Many ORs that detect aliphatic odorants (S19-S86) are located in a distinct branch, which is shaded in gray.