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Fig. 3 | Zoological Letters

Fig. 3

From: The phylum Vertebrata: a case for zoological recognition

Fig. 3

Hox-cluster gene organization in deuterostomes. Colored ovals indicate Hox genes. Genes of smaller paralogous subgroup numbers are to the left and those of larger numbers are to the right. A putative chordate ancestor may have possessed a single Hox gene cluster with ~ 13 genes. This would have been conserved in hemichordates and cephalochordates, although cephalochordates must have undergone duplication of the posterior-most genes. Echinoderms most likely lost Hox6. In urochordates, the Hox cluster was reorganized; in Ciona intestinalis, Hox genes are mapped on two chromosomes and the putative gene order is shown for Hox2 to 4 and Hox5 and 6. Jawed vertebrates, except teleosts, have four Hox gene clusters (HoxA to HoxD from top to bottom), whereas the sea lamprey contains six Hox gene clusters (Hox-α to Hox-ζ). (References are in the text)

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