Phylogenetic tree of all GPCR sequences. A: Visualization of the human entries from the hierarchical tree constructed from the MSA of the TM domains from all sequences in the database. The number indicated after the receptor name equals the number of sequences which are grouped together in the visualized node. Leafs are colored according to the IUPHAR  family definition. B: Detailed view of the hierarchical tree of the branch including the human thyroid stimulating hormone receptor 1 with the leafs colored according to phylogenetic relatedness. C: Distribution of the number of sequences per species grouped together in a node containing one human receptor sequence. The number of missing receptor sequences was calculated with the assumption that each human receptor has one ortholog in each species.