What is RISC and what is its role in RNAi?

• A. RNA-associated silencing complex
• B. RNA interference signaling complex
• C. Ribonucleic acid-induced silencing controller
• D. RNA-induced silencing complex

Answer: (D)

RISC stands for RNA-induced silencing complex, and it is the effector machinery of RNA interference. After double-stranded RNA is processed into small guiding RNAs, one strand is loaded into RISC, where an Argonaute protein uses the guide to recognize complementary messenger RNA. Once bound, RISC can cut the target mRNA if the Ago is slicing-competent, or it can block translation and promote mRNA decay, depending on the context. This is why RISC is central to RNAi—it’s the complex that actually enacts gene silencing by acting on target transcripts. The other phrases don’t reflect the standard name or the functional role of the complex in RNAi, whereas RNA-induced silencing complex correctly names the key effector unit.