Function and specificity of Hox genes.

The Hox genes specify different structures along the anteroposterior axis of bilaterians. They code for transcription factors including a conserved domain, the homeodomain, that binds DNA. The specificity of Hox function is determined by each gene controlling the expression of different groups of downstream genes. These can be other transcription factors, elements in signaling pathways or realizator genes that carry out basic cellular functions. In regulating specific targets, the Hox genes interact with members of signaling pathways and with other proteins, thus forming part of gene networks that contribute to the modification of homologous structures or to the creation of new organs.