Return to the RNAi World: Rethinking Gene Expression and Evolution

While investigating the genetic workings of the microscopic worm, C. elegans, Mello and colleague Andrew Fire, PhD, of the Carnegie Institution of Washington, discovered RNAi, a natural but previously unrecognized process by which a certain form of RNA can be manipulated to silence—or interfere with—the expression of a selected gene. The discovery, published in the journal Nature in 1998, has had two extraordinary impacts on biological science. One is as a research tool: RNAi is now the state-of-the-art method by which scientists can knock out the expression of specific genes in cells, to thus define the biological functions of those genes.