enhancement mutual enhancement 2013-06-05T20:31:30Z An effect in which individual perturbations of different genes result in the same mutant phenotype (but, perhaps, to varying degrees of severity/penetrance) and the resulting phenotype of their combination is more severe/penetrant (further from wild type) than 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 < a* <= b < wt [E = a*] OR wt < b <= a* < ab [E = a*] where 'a' and 'b' are the observed phenotype values of the individual perturbations ('a*' being the most severe of the two), '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:1278 PSI-MI orchard