Figure 4.—

Dependence of heritable silencing on injected trigger concentration. We tested a fivefold serial dilution of the dsRNA induction trigger using the same pedigree selection scheme described in Figure 2. At each concentration, we picked three injected animals to select 14 F₁ animals, placed them on individual plates, and incubated for 3 days at 23°. We used the same criteria to select the descendant populations. We found animals injected with concentrations of 50 to 0.4 ng/μl had an equivalent silencing response: all animals scored in generations F₁, F₂, and F₃ had viable progeny, while all animals of the F₄ generation had no viable progeny. Silencing efficacy of concentrations of 0.08 and 0.016 ng/μl were less effective at both the overall silencing frequency (<100%) and in the persistence of the silencing response. Animals injected with 0.0032 ng/μl showed no silencing response.