Arthropod Hox genes: insights on the evolutionary forces that shape gene functions

Comparative studies suggest that gene duplication, changes in cis-regulatory elements and changes in protein sequence all contribute to the evolution of Hox gene functions, but the evolutionary dynamics of these changes are probably different. It seems likely that gene duplications arise as neutral changes and acquire an adaptive significance later on. By contrast, some changes in regulatory and protein-coding sequences can have immediate consequences in morphological evolution.