RNA interference is a process in which translation of some of a cell's messenger RNA (mRNA) sequences is prevented, because of the presence of (and consequent destruction of) matching double-stranded RNA sequences. RNA interference is believed to protect the cell against viruses and other threats. "Interference" refers to the interruption of the cell's translation of its own mRNA. RNA interference is also called posttranscriptional gene silencing, since its effect on gene expression occurs after the creation of the mRNA during transcription.

RNA interference has been found in plants, fungi, and a variety of animals, including the roundworm (Caenorhabditis elegans), fruit fly (Drosophila melanogaster), zebrafish, and mouse. It is believed to be an ancient form of defense. It may also explain some or most of the gene-silencing effect of "antisense" RNA, as discussed elsewhere in this encyclopedia.

Dicing Up Dsrna

Under most circumstances, RNA in a cell...