Edward J. Louis1
Single genes, chromosomal regions and even entire genomes can undergo duplication. What good can come of these extra copies? Evolution seems to use several tricks to take advantage of the situation.
Gene mutations often result in abnormal levels or function of their protein products. Consequently, the divergence rate of DNA sequences that encode genes is generally slower than that for non-coding sequences. So how does new genetic material arise? One valuable source is sequences formed through gene and genome duplication events.
The commonest consequence of genomic duplication seems to be the loss of all or part of duplicated sequences through deletion1 or degeneration2, causing non-functionality. This can be a powerful evolutionary force — for example, gene loss in response to whole-genome duplication led to rapid speciation in yeast3. Alternatively, although it is much less-well understood, one or both of the duplicated sequences might acquire new functions, as they are under less selective pressure, and can afford to undergo mutations that would lead to new characteristics and functions. On page 677 of this issue, Hittinger and Carroll4 analyse one such pair of duplicated genes with divergent functions.
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