Practice question

Small interfering RNA pathway uses near-perfect complementarity guiding Argonaute degradation. Upon RISC loading and passenger ejection, guide strand pairs extensively with viral or transposon transcripts positioning scissile bond at Ago PIWI active site for cleavage between positions ten and eleven. Cleaved fragments rapidly degraded by Xrn1 5'-3' and exosome 3'-5', preventing translation. In plants, worms, fungi secondary amplification by RdRP generates additional siRNAs spreading silencing. Extensive pairing ensures specificity distinguishing siRNA from miRNA tolerating mismatches. This mechanism underlies knockdown technology using synthetic siRNA duplexes to deplete mRNAs for functional genomics and therapeutic gene silencing approaches widely.