When Mother Nature creates an identical copy of a gene in an organism's genome, the duplicated copy is usually deleted, inactivated, or otherwise rendered nonfunctional in order to prevent genetic redundancy and to preserve biological homeostasis. In some cases, however, gene duplicates are maintained in a functional state. Until now, the biological and evolutionary forces behind the maintenance of these duplicates as functional components of the genome have remained unclear.
To determine the basis for the persistence of functional gene duplicates in the genome, three scientists at the Institute of Molecular Systems Biology at the Swiss Federal Institute of Technology in Zürich have collaborated on the largest systematic analysis of duplicated gene function to date. Using an integrative combination of computational and experimental approaches, they classified duplicate pairs of genes involved in yeast metabolism into four functional categories:
- back-up, where a duplicate gene copy has acquired the ability to compensate in the absence of the other copy,
- subfunctionalization, where a duplicate copy has evolved a completely new, non-overlapping function,
- regulation, where the differential regulation of duplicates fine-tunes pathway usage, and
- gene dosage, where the increased expression provided by the duplicate gene copy augments production of the corresponding protein.
Their results, which appear in the October issue of the journal Genome Research, indicate that no single role prevails but that all four of the mechanisms play a substantial role in maintaining duplicate genes in the genome.