Gene structure of the platypus α- and β-globin clusters and flanking loci, and comparisons of their promoter regions with other mammals. (A) The platypus α-globin cluster contains six α-like globin genes (red), a β-like (ω) globin gene (blue) and a distantly related globin gene, GBY (green), which are flanked by IL9RP3-POLR3K-C16orf33-C16orf8-MPG-C16orf35 on the 5' end and LUC7L-ITFG3-RGS11-ARHGDIG-PDIA2-AXIN1 on the 3' end (black). The platypus β-globin cluster contains only two genes, ε and β (blue), which are flanked on both sides by ORG genes (black). (B) Relative positions of the putative transcription factor binding sites in the 200 bp promoter region located upstream of the predicted platypus, marsupial (Didelphis virginiana ζ and ψζ', and Sminthopsis macroura αD, ψα3, α2, α1, ω, ε and β) and human α- and β-like globin genes. For the platypus GBY no data was available from other species, including Xenopus tropicalis, for comparisons.