Essential for RNA interference (RNAi); double-stranded RNA (dsRNA) induces potent and specific gene silencing. RNAi is mediated by the RNA-induced silencing complex (RISC), a sequence-specific, multicomponent nuclease that destroys or silences messenger RNAs homologous to the silencing trigger. May carry out the initiation step of RNAi by cleaving dsRNA to produce 22 bp dsRNAs (siRNAs) which target the selective destruction of homologous RNAs. During embryogenesis, involved in germline fate determination. Interacts with AGO2 and Fmr1 to form the RNA-induced silencing complex (RISC), a ribonucleoprotein (RNP) complex involved in translation regulation; other components of the complex are RpL5, RpL11, AGO2 and Rm62 (PubMed:11498593, PubMed:12368261). Interacts with piwi and vas; these interactions occur in the polar granules (PubMed:16949822). Belongs to the helicase family. Dicer subfamily.