A conserved biological response to double-stranded RNA, known variously as RNA
interference (RNAi) or post-transcriptional gene silencing, mediates resistance to both
endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the
expression of protein-coding genes. RNAi has been cultivated as a means to manipulate
gene expression experimentally and to probe gene function on a whole-genome scale.