A: Vertebrate genomes were searched for the presence of the 57 bp Rac1b-specific exon. For each considered species is shown the predicted peptide, the position of the additional exon upstream of the normal 4th Rac1 exon, and the size of the third exon. B: RhoD and RhoF homologues were searched in mouse (Mm), dog (Cf), pig (Ss), opossum (Md), platypus (Oa) and chicken (Gg) and aligned with human sequences using ClustalX. Human Cdc42 and RhoA were included as external outgroups.