Mechanisms of RNA interference. After the introduction of dsRNA into a target cell, the dsRNA is processed into siRNA length of 21-23 nucletides by Dicer. siRNA then enters an RNA-induced silencing complex (RISC) assembly pathway. The dsRNA unwinds to form two single-strands of RNA. The passenger strand rapidly degrades and the guide strand binds and cleaves the target mRNA, resulting in mRNA degradation.