Small interfering RNA (siRNA), also known as short interfering RNA, is a class of 20-29 nucleotide, double-stranded RNA molecules that play a variety of roles in biological processes. siRNAs were initially discovered to be involved in the RNA interference (RNAi) pathway, silencing the expression of specific genes through post-transcriptional mechanisms. Recent studies demonstrate that siRNAs also act in other RNA related pathways, such as anti-viral mechanisms and shaping the chromatin structure in a genome. The complexity of these pathways has only recently been elucidated.
Since the initial demonstration of its functionality in mammalian cells, siRNA technology has been an indispensable tool in functional genomics and has been predicted to become a novel form of future medicine.