Relationships of the N-domains of dog CEA gene family members. (A) The mature N domain amino acid sequences of the dog CEACAM1-related CEA family members were aligned using the ClustalW program provided at the NPS server. Identical amino acids are shown in red, conservatively exchanged amino acids in blue and green and non-conservative changes in black. (B) The amino acid sequence positions which differ between CEACAM1 and the CEACAM1-related N domains (shown in red) are mapped to 3-D ribbon models calculated using the Geno3D-release 2 program. The models are shown with the CFG sheet in front (left model) and facing to the left (right model). (C) The ratios of non-synonymous and synonymous mutation in the N domain exons (small black numbers at the branches of the dendrogram) are close to one or higher (except for the nearly identical CEACAM1 and CEACAM28 sequences). This indicates selective pressure for divergence of N domain sequences during evolution. Hsa, Homo sapiens; Cfa, Canis familiaris.