converging genetic interaction positive genetic interaction PSI-MI Positive interactions describe double mutants exhibiting a less severe phenotype than expected from the multiplicative model. Positive interactions have also been referred to as alleviating or epistatic interactions. Positive genetic interactions define double mutants whose phenotype is less severe than expected based on single-mutant phenotypes (30, 66, 87) (Figure 1c,d). An effect in which two genetic perturbations, when combined, result in a fitness that is greater than expected given the fitness resulting from the individual perturbations. MI:2395 alleviating interaction positive gent int