Figure 7.—

Comparison of silencing transmission capacity for oocytes and sperm. (A) Genetic scheme. We first selected one injected animal (I₀) to produce F₁ and F₂ descendants by self-fertilization. We then selected one F₂ animal with a large brood size to separately assess sperm and oocyte transmission of silencing. (B) Results of sperm/oocyte comparison. F₃ cross-progeny animals were scored individually (7 animals for oocyte transmission and 6 for sperm transmission). F₄ descendants were scored in groups of siblings rather than individually since our previous experiments (Figure 2) indicated a consistent F₄ bottleneck. In the oocyte experiments, only 2 of 7 F₃ animals had progeny: 1 animal had 48 progeny and 1 animal had 1 progeny. None of the F₄ animals had F₅ progeny. In contrast, in the sperm-transmission experiments, all 6 F₃ animals had viable progeny, with brood sizes ranging from 28 to 80. We used groups of F₄ animals from sperm transmission and found 26/26 plates with 10 animals to a plate to have viable progeny. To analyze the F₅ silencing, we checked the F₄ plates for fertile F₅ animals. We found 2/26 plates with viable F₅ progeny.