Illustration of the US geneticist Craig Mello (born 1960). Mello is best known for the discovery, along with his colleague Andrew Fire, of RNA interference (RNAi). RNA (ribonucleic acid) is the intermediary molecule between a gene and its protein product. A genes DNA (deoxyribonucleic acid) is transcribed to messenger RNA (mRNA), which is translated to the protein sequence. RNAi, also known as post-transcriptional gene silencing, is a process whereby small RNA molecules bind to mRNA, preventing it from being translated and so inhibiting the expression of the gene. Mello and Fire received the 2006 Nobel Prize in Physiology or Medicine for their discovery.