PARALOGOUS HOX GENES - FUNCTION AND REGULATION

The Hox homeobox gene family plays a pivotal role in regulating patter ning and axial morphogenesis in vertebrates. Molecular characterizatio n of the four Hox clusters has shown that they are evolutionarily rela ted with respect to sequence, organization, and expression, suggesting they arose by duplication and divergence. Transgenic analysis has cle arly demonstrated the functional roles of individual genes in a broad range of embryonic tissues, and in compound mutants has addressed the issues of cooperativity and redundancy. There is an emerging picture o f the cis-regulatory elements underlying Hox expression, and for the 3 ' members of the clusters there is a considerable degree of conservati on between paralogous genes with respect to their functional roles and regulatory control.