Evolutionary scenario for the vertebrate SSTR gene-bearing chromosome regions. Two ancient vertebrate chromosomes bearing one SSTR gene each duplicated in 2R, generating two vertebrate paralogons; one bearing SSTR1, -4 and -6 genes (purple, pink, blue and turquoise blocks) and one bearing SSTR2, -3 and -5 genes (red, yellow, orange and green blocks). After the divergence of lobe-finned fishes (including tetrapods) and ray-finned fishes (including teleosts), three of the 2R-generated blocks fused in the ray-finned fish lineage before 3R. Both paralogons duplicated in 3R, followed by rearrangements between paralogous chromosome blocks, obscuring the ancestral conserved synteny. One of the fused, duplicated and rearranged chromosome blocks split through a fission event. The paralogous chromosome regions have been reconstructed for the chicken, human and medaka genomes by mapping the identified paralogous gene families. The upper color blocks represent ancestral chromosome regions in each lineage. Dashed boxes represent losses of chromosome blocks. Chromosome rearrangements involving blocks of genes are represented by arrows, while smaller translocations of genes are represented by dashed arrows. The full datasets are presented in Tables S4 and S5 (see Additional files 3 and 4).
Ocampo Daza et al. BMC Evolutionary Biology 2012 12:231 doi:10.1186/1471-2148-12-231