Fig. 5. Quantitation of embryonic (A) and larval (B) lethality in vab-1 efn double mutants. vab-1; efn double mutants were constructed and lethality quantitated as described in the Materials and Methods. All vab-1; efn-4 double mutants (black bars) showed significantly enhanced lethality compared with the relevant single mutants (white bars). vab-1(0); efn-4 double mutants were fully lethal and maintained as balanced strains of genotype vab-1/mIn1 mIs14; efn-4. vab-1(e2); efn-4 and vab-1(e699); efn-4 double mutants were >96% lethal, with rare escapers; among these escapers, 30-50% were fertile with average brood sizes of 24 and 51, respectively. Data for vab-1; efn-1 double mutants, included for comparison, are taken from Chin-Sang et al. (Chin-Sang et al., 1998). efn-2 mutations significantly increase the embryonic lethality and significantly decrease the larval lethality of vab-1(0) mutants. efn-2 mutations also significantly enhanced the embryonic and larval lethal phenotypes of vab-1(kinase) mutations, a result that contrasts with the lack of enhancement of vab-1(kinase) male tail phenotypes by efn-2 (Wang et al., 1999). vab-1; efn-3 double mutants were not significantly different from vab-1 controls. Error bars indicate the s.e.m. Differences in penetrance between vab-1 and vab-1; efn strains were compared using ANOVA; ^*, P<0.05; ^**, P<0.01.