In Brief

RNA interference: Silencing of the genes

The Human Genome Project identified all human genes, but it didn't tell us what each of these genes do or how to turn them on and off. The 2006 Nobel Prize in Physiology or Medicine was awarded to Andrew Fire and Craig Mello for their studies of a powerful technology called RNA interference — RNAi for short — that is helping scientists do just that, and it may provide doctors with a way to switch off the genes that cause disease.

Every cell in your body has the same set of genes. Yet a cell, say, in your stomach that's churning out acid acts — and looks — nothing like a cell in your eye that reacts to light. The reason that genetically identical cells can be so different from one another is the variability in the genes that are "turned on" and active. Every active gene makes a protein. Scientists have discovered that cells make very short strands of RNA, called microRNAs, which can stop the ability of a particular gene to make a particular protein — effectively "silencing" the gene. The field of RNA interference was born.