Practice question

MicroRNAs are endogenous 21-22 nucleotide regulators processed from stem-loops by Drosha and Dicer that typically pair imperfectly, especially central bulges, with 3' UTR target sites. Imperfect pairing prevents Ago2 slicing; instead recruits GW182 scaffold bridging Argonaute to CCR4-NOT deadenylase and DDX6 helicase causing translation inhibition interfering with eIF4F cap recognition, 60S joining, or elongation. Concurrently triggers deadenylation, decapping, and decay or P-body sequestration. This tunable repression coordinates multiple targets regulating development, cell cycle, metabolism, contrasting siRNA perfect pairing triggering direct cleavage and immediate mRNA destruction providing nuanced regulatory control over protein output.