Evolution by gene duplication revisited: differentiation of regulatory elements versus proteins.

For evolution by gene duplication, differentiation of both regulatory elements and proteins is important. Particularly the former is thought to have large effects on morphological evolution, since differential expression of genes is essential for development. In this report, recent knowledge on regulatory elements is reviewed that is relevant to the population genetics aspects of gene duplication. Regulatory elements usually consist of multiple binding sites of two or more transcription factors. The amount of gene product is quantitatively regulated, and is thought to be subject to stabilizing selection. The intensity of stabilizing selection depends upon the level of constraint imposed by regulatory networks. Gene duplication has significant effects on stabilizing selection via perturbation of gene expression. It is pointed out that constraints coming from regulatory networks are most important for survival of duplicate genes, and that both drift and selection are at work in the process of acquisition of new gene expression and function.