Mutational fitness effects in RNA and single-stranded DNA viruses: common patterns revealed by site-directed mutagenesis studies

Philos Trans R Soc Lond B Biol Sci. 2010 Jun 27;365(1548):1975-82. doi: 10.1098/rstb.2010.0063.


The fitness effects of mutations are central to evolution, yet have begun to be characterized in detail only recently. Site-directed mutagenesis is a powerful tool for achieving this goal, which is particularly suited for viruses because of their small genomes. Here, I discuss the evolutionary relevance of mutational fitness effects and critically review previous site-directed mutagenesis studies. The effects of single-nucleotide substitutions are standardized and compared for five RNA or single-stranded DNA viruses infecting bacteria, plants or animals. All viruses examined show very low tolerance to mutation when compared with cellular organisms. Moreover, for non-lethal mutations, the mean fitness reduction caused by single mutations is remarkably constant (0.10-0.13), whereas the fraction of lethals varies only modestly (0.20-0.41). Other summary statistics are provided. These generalizations about the distribution of mutational fitness effects can help us to better understand the evolution of RNA and single-stranded DNA viruses.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • DNA Viruses / genetics*
  • DNA, Single-Stranded / genetics*
  • Evolution, Molecular*
  • Mutagenesis, Site-Directed / methods*
  • RNA Viruses / genetics*


  • DNA, Single-Stranded