Fig. 1.

Different definitions of genetic interaction lead to different distributions of ε (the deviation of the observed double-mutant fitness from expectation). (A) Distributions from all reproducibly measured pairs from Study J that involve genes with singly deleterious mutations show the Min definition to have a negative bias and clear differences from other definitions. (B) The subset of pairs from A involving genes with minor fitness effects shows no significant differences between definitions. (C) The subset of pairs from A involving genes with moderate fitness effects shows Min to have the most severe bias in ε. (D) The subset of pairs from A involving at least one extreme fitness defect exhibits a positive shift in bias in ε for definitions.