RNA interference operates by which mechanism?

• A. It degrades DNA at the target locus.
• B. It silences gene expression by degrading mRNA or blocking translation using small interfering RNAs or microRNAs.
• C. It promotes chromosomal translocations.
• D. It integrates viral DNA into the genome.

Answer: (B)

RNA interference uses small RNA guides to silence gene expression at the mRNA level. Dicer processes double-stranded RNA or hairpin precursors into siRNAs or miRNAs, which are loaded into the RNA-induced silencing complex. The guide strand directs the complex to a complementary mRNA, and the Argonaute component either cleaves the mRNA or blocks its translation, reducing the amount of protein produced. This is a post-transcriptional mechanism that changes gene expression without altering the DNA sequence. It doesn’t degrade DNA at the target locus, promote chromosomal translocations, or integrate viral DNA.