ParaHox
The ParaHox gene cluster is an array of
Regulatory gene cluster
These genes were first shown to be arranged into a physically-linked chromosomal cluster in
The ParaHox gene cluster has been proposed to be a paralogue, or evolutionary sister, of the Hox gene cluster;[1] the two gene clusters being descendent from a segmental duplication early in animal evolution, preceding the divergence of cnidarians and bilaterian animals.[5] It has been suggested that an ancient role of the ParaHox gene cluster in bilaterians was the specify or pattern the through-gut, with Gsx patterning the mouth, Xlox (=Pdx) patterning the midgut and Cdx marking the anus.[6][7] Gene expression and functional data lends tentative support to this hypothesis,[7][8] although in many animals the roles of the genes have changed in evolution, notably the Gsx gene family which plays a role in brain (not foregut) development in vertebrates.[9]