Department of Biology, University of New Mexico, 167A Castetter Hall, Albuquerque, NM 817131-1091, USA. wagnera@unm.edu
Immediately after a gene duplication event, the duplicate genes have redundant functions. Is natural selection therefore completely relaxed after duplication? Does one gene evolve more rapidly than the other? Several recent genome-wide studies have suggested that duplicate genes are always under purifying selection and do not always evolve at the same rate.