Figure 1

Conservation of synteny of OR genes. (a) All ORs from each species are ordered along the axis according to their genomic location from chromosome 1 to X (or by scaffold number in the case of the opossum), and by the internal megabase coordinates in each chromosome. Each point represents an alignment between two ORs from different species in the UCSC alignment net, colored according to the degree of DNA sequence identity (x-axis for the reference species, y-axis for the target species). Diagonals in both directions represent conservation of gene order, whereas reverse diagonals indicate a reverse of gene order relative to the 'plus' DNA strand. Off-diagonal points generally indicate micro-rearrangements, but those that are associated with low percentage identity possibly represent alignment errors. (b) Zoomed human versus mouse comparison, with chain numbers (by UCSC hg17 versus mm6 alignment net) indicated for the 16 alignment chains that contain at least six pairs of syntenic orthologs. Chains #95 and #183 represent disrupted synteny, because the alignment of a succession of ORs from human chromosome 6 is split between mouse chromosomes 13 and 17 (as described by Amadou and coworkers [26]). Chains #375 and #118 capture a genomic inversion. OR, olfactory receptor.