Figure 3.

The major septal olfactory receptor genes fall into a few subfamilies in an unrooted phylogenetic tree of the mouse olfactory receptors. The full-length protein sequences of 893 mouse olfactory receptors (Zhang and Firestein, 2002) were aligned using web-based ClustalW, and the resulting multiple alignment was used as input for TreeExplorer to generate the tree. The major septal olfactory receptor genes are in thick and dark lines. The Class I receptors are labeled, and the remaining belong to Class II.