siRNA (small interfering RNA), also named as short interfering RNA or silencing RNA, is a class of double-stranded RNA molecules (usually 20 to 24 bp). Structurally, siRNA has phosphorylated 5' ends and hydroxylated 3' ends with two overhanging nucleotides. The Dicer enzyme catalyzes the production of siRNA from long dsRNA and small hairpin RNA. The siRNA operates within the RNA interference (RNAi) pathway, which interferes with the expression of particular genes with complementary nucleotide sequences by post-transcriptional degradation of mRNA, thereby preventing translation.