Jul 30, 2005

Perspective: Sign epistasis and genetic constraint on evolutionary trajectories

Evolution; International Journal of Organic Evolution
Daniel M WeinreichLin Chao

Abstract

Epistasis for fitness means that the selective effect of a mutation is conditional on the genetic background in which it appears. Although epistasis is widely observed in nature, our understanding of its consequences for evolution by natural selection remains incomplete. In particular, much attention focuses only on its influence on the instantaneous rate of changes in frequency of selected alleles via epistatic contribution to the additive genetic variance for fitness. Thus, in this framework epistasis only has evolutionary importance if the interacting loci are simultaneously segregating in the population. However, the selective accessibility of mutational trajectories to high fitness genotypes may depend on the genetic background in which novel mutations appear, and this effect is independent of population polymorphism at other loci. Here we explore this second influence of epistasis on evolution by natural selection. We show that it is the consequence of a particular form of epistasis, which we designate sign epistasis. Sign epistasis means that the sign of the fitness effect of a mutation is under epistatic control; thus, such a mutation is beneficial on some genetic backgrounds and deleterious on others. Recent experiment...Continue Reading

  • References27
  • Citations233

References

  • References27
  • Citations233

Mentioned in this Paper

Genetic Drift
Biochemical Pathway
Chaos
Mutagenesis, Site-Directed
Dysequilibrium Syndrome
Bacteriophages
Genetics, Population
Recombination, Genetic
Sample Fixation
Deleterious Mutation

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