Two U.S. scientists have been honored the Nobel Prize for medicine for their discovery of RNA interference that controls the expression of genes. Their groundbreaking work in genetics could lead to new treatments for illnesses such as viral infections and cancer.

Dr. Andrew Fire and Dr. Craig Mello's research could potentially aid researchers to turn off harmful genes and systematically experiment with the functions of all human genes.

Dr. Craig Mello is from the University of Massachusetts Medical School while Dr. Fire is from Stanford University School of Medicine.

The Nobel citation, issued by Sweden's Karolinska Institute, said: "This year's Nobel Laureates have discovered a fundamental mechanism for controlling the flow of genetic information."

Professor Nick Hastie, director of the Medical Research Council's Human Genetics Unit, said the fact that the work had been recognized by a Nobel Prize only eight years after it was published indicated just how important it had been.

He said: "It is very unusual for a piece of work to completely revolutionize the whole way we think about biological processes and regulation, but this has opened up a whole new field in biology."