TABLE 1.

SL1 driven by the U2-3 promoter can rescue lethality^a

Construct	No. of rescued lines/total no. of lines	% Rescue of wDf1 embryonic lethality (n)b	Embryonic rescuec
None	NA	0 (2,039)e	NA
SL1-SL1 promoter	4/5d	49 (1,394)e	+
SL1-U2 promoter	6/7d	54 (2,525)	+

^aNA, not applicable. Heterozygous animals of the genotype unc-76 (e911) wDf1 / unc-61 (e228) dpy-21 (e428) were used in transformation experiments (see Materials and Methods). 

^bn, total number of progeny counted, including arrested embryos and larvae. Percent rescue was calculated by the formula 100[1 − (average percent arrested embryos observed/average percent arrested embryos from the parental strain)]. The average percent arrested embryos for the wDf1 parental line was 25.3%, as expected for heterozygotes carrying a recessive lethal mutation (see Materials and Methods). 

^cEmbryonic rescue was scored as “+” if the average percentage of arrested embryos was below 20% and arrested elongated embryos and/or extra Unc-76 larvae (defined as significantly greater than the ∼2% of Unc-76 recombinants usually observed in the parental strain) were observed. (Since the unc-76 mutation is linked in cis to the lethal wDf1 mutation, Unc-76 animals are infrequently observed in the parental strain [12].) 

^dLines that showed no apparent rescue were not used in the calculation of percent rescue. 

^eAs reported in reference 12.