RNA interference (RNAi) is a mechanism of gene expression involving double-stranded ribonucleic acid (RNA). Double-stranded RNA (or dsRNA), as is seen here, can be used to block the expression of specific genes. The RNAi pathway evolved in primitive single-celled organisms to prevent RNA viruses from replicating successfully. Research scientists are now experimenting with the idea that artificially introduced dsRNA from a disease gene can prompt the RNAi process to silence that gene, just as it would silence the genes of a naturally acquired virus. In addition, it is an important research tool, as synthetic dsRNA introduced into cells can induce suppression of specific genes of interest.