diverging genetic interaction negative genetic interaction An effect in which two genetic perturbations, when combined, result in a fitness that is less than expected given the fitness resulting from the individual perturbations. synergistic interaction aggravating interaction MI:2394 negative gen int Negative interactions (also called aggravating or synergistic interactions) describe double mutants exhibiting a more severe phenotype than expected, such as synthetic sickness or synthetic lethality (35, 49) (Figure 2a). Negative genetic interactions describe double mutants whose phenotype is stronger than expected (66, 77) (Figure 1b). PSI-MI