Phylogenetic analysis of Iroquois family members. The neighbor-joining tree was calculated from Kimura distances, with scale bars indicating the percentage (x 1/100) of sequence divergence. Numbers above branches indicate the number of times (%) the branch was found in 200 bootstrap replicates. Bootstrap values at short external branches (<2% divergence) are not indicated. The gene tree was inferred from the amino acid alignment in Fig. 2 A (positions 128–256), analyzing a set of 21 vertebrate genes, 3 genes fromDrosophila and the Caenorhabditis elegans geneC36F7.1, which was used as the outgroup. Incomplete sequences (chicken Irx3, rat Irx4) have not been considered. Brackets at the right highlight the clustering of vertebrate genes into six orthologous groups.