RNA interference: the next genetics revolution?
Safia Wasi

Figure 1 | RNAi-mediated gene silencing.
RNA interference (RNAi) is an apparently ancient defence mechanism against foreign double-stranded RNA (dsRNA). RNAs of just 22 nucleotides in length, called small interfering RNAs (siRNAs), are snipped from longer dsRNA chains by an enzyme called Dicer. The antisense strand of the siRNA is used by an RNA-induced silencing complex (RISC) to guide messenger RNA (mRNA) cleavage, so promoting mRNA degradation.
Modified with permission from McManus, M. T. & Sharp, P. A. Gene silencing in mammals by small interfering RNAs. Nature Rev. Genet. 3, 737-747 (2002) © Macmillian Magazines Ltd. miRNA, microRNA; stRNA, small temporal RNA.