RNA interference (RNAi) is a biological process in which RNA molecules are involved in sequence-specific suppression of gene expression by double-stranded RNA, through translational or transcriptional repression. RNAi has an important role in defending cells against parasitic nucleotide sequences such as viruses or transposons and also influences the development of organisms. RNAi is a valuable research tool, both in cell culture and in living organisms, because synthetic dsRNA introduced into cells can selectively and robustly induce suppression of specific genes of interest. RNAi may be used for large-scale screens that systematically shut down each gene (and the subsequent proteins it codes for) in the cell, which can help to identify the components necessary for a particular cellular process or an event such as cell division.

RNAi is an RNA-dependent gene silencing process that is controlled by RISC and is initiated by short double-stranded RNA molecules in a cells cytoplasm, where they interact with the catalytic RISC component Argonaute. When the dsRNA is exogenous (coming from infection by a virus with an RNA genome or laboratory manipulations), the RNA is imported directly into the cytoplasm and cleaved to short fragments by Dicer. RNAi is a vital part of the immune response to viruses and other foreign genetic material, especially in plants where it may also prevent the self-propagation of transposons.

RNAi has a guide or search engine capability that enables scientists to find specific genetic data in a library filled with billions of books, where each book represents one persons DNA. RNAi can be programmed to find a genetic defect and silence it, which shows fascinating promise as a tool in molecular biology. RNAi therapeutics is an innovative new class of medicines based on RNA interference (RNAi) that may become an important weapon against increasingly antibiotic-resistant bacterial.