Fig. 7. Quantitation of genetic interactions between efn-4 and mab-20. Penetrance of embryonic lethality (A) and larval lethality (B) in mab-20 (white bars) and in mab-20 efn-4 double mutants (black bars). Error bars indicate the s.e.m. Differences in penetrance between mab-20 and mab-20; efn-4 strains were compared using ANOVA; ^*, P<0.05; ^**, P<0.01. mab-20 strains exhibited 20-30% embryonic lethality depending on the allele; in all mab-20; efn-4 strains, the penetrance of embryonic lethality was not significantly different compared with the mab-20 single mutant. Most mab-20; efn-4 double mutant strains displayed significantly increased larval lethality, consistent with additivity of mutant phenotypes.