Difference of tissue-specificity between orthologs and paralogs.

Each bar represents the number of gene pairs of a given type for a given phylogenetic age, for which both genes of the pair are tissue-specific (τ > 0.8). In dark color, the number of gene pairs specific to the same tissue; in light color, the number of gene pairs specific to different tissues. Orthologs are in red, in the left panel, paralogs are in blue, on the right panel; notice that the scales are different for orthologs and for paralogs. Orthologs are one-to-one orthologs to human and paralogs are within-species paralogs in human. The overall proportions of pairs in the same or different tissues are indicated for orthologs and paralogs; in addition, for paralogs the proportion for pairs younger than the divergence of tetrapods (whole genome duplication) is also indicated.