Figure 1.

Classification of olfactory receptors. (a) An unrooted phylogenetic tree, reproduced with permission from [15]. Positions of olfactory receptor genes on chromosomes 11 (green) and 1 (red) are highlighted, and the scale bar corresponds to 10% sequence divergence. (b) The relative sizes of the various olfactory receptor gene families, reproduced with permission from [16]. Colors and numbers denote individual families, and those denoted UC are unclassified.