negative genetic interaction enhancement 2013-06-05T19:12:17Z Aggravating interaction An effect in which the phenotype of one genetic perturbation is enhanced by a second perturbation to a severity/penetrance beyond (further from wild type) that expected by the superimposition or addition of effects of the individual perturbations. With respect to any single quantifiable phenotype, this may be expressed as an inequality as: ab < E < wt OR wt < E < ab where 'ab' is the observed phenotype value of the double perturbation, 'E' is the expected phenotype value of the double perturbation, and 'wt' is the wild type phenotype value. MI:1271 PSI-MI orchard