Explain the mechanism of RNA interference (RNAi).

RNA interference is a gene silencing mechanism triggered by double-stranded RNA. The enzyme Dicer cleaves dsRNA into small interfering RNAs (siRNAs) of 21-23 nucleotides. These siRNAs are loaded into the RNA-induced silencing complex (RISC), where Argonaute proteins unwind the duplex and retain the guide strand. The guide strand directs RISC to complementary mRNA targets, leading to mRNA cleavage or translational repression. MicroRNAs (miRNAs) work similarly but typically cause translational inhibition through partial complementarity. RNAi is used for gene knockdown studies and has therapeutic potential.