Gene function, gene networks and the fate of duplicated genes

For both copies of a duplicated gene to become fixed in a population and su bsequently maintained selection must favour individuals with both genes ove r individuals with one. Here I review and assess some of the proposed ways that gene structure and function might affect the likelihood of both copies acquiring distinct functions and therefore positive selection. In particul ar I focus on the interacting pathways of genes that make up gene networks, and how these may affect genes duplicated both singly and en masse. Using the Wnt and hedgehog pathways as examples and data from developmental and g enome analyses, I show that, while some of these theories may genuinely ref lect what has occurred in animal evolution, there are still insufficient da ta to rigorously assess their relative importance. This, however, is likely to change in the near future.