directional epistasis
Sanjuán R & Elena SF 2006 Epistasis correlates to genomic complexity. PNAS 103:14402-14405.
- simpler genomes, such as those of RNA viruses, display antagonistic epistasis (mutations have smaller effects together than expected)
- bacterial microorganisms do not apparently deviate from independent effects
- in multicellular eukaryotes, a transition toward synergistic epistasis occurs (mutations have larger effects together than expected)
- antagonistic epistasis might be a property of compact genomes with few nonpleiotropic biological functions
- in complex genomes, synergism might emerge from mutational robustness
