Fig. 5.

Distinct types of modifier architecture involved in conditional essentiality. Colors indicate the genetic backgrounds from which the modifier loci were mapped (yellow, S288c; blue, Σ1278b; and green, Y12). Different genetic backgrounds are highlighted in color-coded ovals. Example cases for each proposed scenario are indicated at the Top of each panel. (A) Conditional essentiality related to independent genes and multiple allelic variants across different background. (B) Conditional essentiality related to independent loci in the same background, each locus alone is sufficient to suppress the lethal phenotype. (C) Combination of multiple loci in the same background suppress lethal phenotype. All loci are required simultaneously. (D) Novel allelic combination arose from hybrid of different strain backgrounds led to suppression of the lethal phenotype.