Figure 5.

Protein-coding gene order comparison of the mtDNAs from the pterobranch Rhabdopleura compacta to the enteropneusts, Xenoturbella bocki, the ground pattern of echinoderms and the consensus arrangement of vertebrates. Genes located above the middle line are transcribed from the heavy strand whereas those located below the middle line are transcribed from the light strand. The question marks indicate the unknown ancestral strand affiliation of the fragment containing the ND1 and ND2 genes in echinoderm genomes (see [11]). Rearrangement steps between the gene orders are marked by grey straight lines (transpositions) and grey crossed lines (inversions).