Letters to Nature

Nature 388, 167-171 (10 July 1997) | ; Received 14 January 1997; Accepted 25 April 1997

Evolution of genetic redundancy

Martin A. Nowak1, Maarten C. Boerlijst1, Jonathan Cooke2 and John Maynard Smith3

  1. Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, UK
  2. National Institute for Medical Research, The Ridgeway, London NW7 1AA, UK
  3. School of Biological Sciences, University of Sussex, Brighton BN1 9QG, UK

Correspondence to: Martin A. Nowak1 Correspondence should be addressed to M.A.N.
(e-mail: Email: martin.nowak@zoo.ox.ac.uk).

Genetic redundancy means that two or more genes are performing the same function and that inactivation of one of these genes has little or no effect on the biological phenotype. Redundancy seems to be widespread in genomes of higher organisms1, 2, 3, 4, 5, 6, 7, 8, 9. Examples of apparently redundant genes come from numerous studies of developmental biology10, 11, 12, 13, 14, 15, immunology16,17, neurobiology18,19 and the cell cycle20,21. Yet there is a problem: genes encoding functional proteins must be under selection pressure. If a gene was truly redundant then it would not be protected against the accumulation of deleterious mutations. A widespread view is therefore that such redundancy cannot be evolutionarily stable. Here we develop a simple genetic model to analyse selection pressures acting on redundant genes. We present four cases that can explain why genetic redundancy is common. In three cases, redundancy is even evolutionarily stable. Our theory provides a framework for exploring the evolution of genetic organization.