"The Nobel Assembly at Karolinska Institute has today decided to award the Nobel Prize in Physiology or Medicine for 2006 jointly to Andrew Fire and Craig Mello for their discovery ofRNAinterference, gene silencing by double-stranded RNA," he said.

Fire from Stanford University and Mello from the University of Massachusetts published their groundbreaking work in the journal, Nature, in 1998.

Their work centered on discovering a method of turning off selected genes - an important new tool that fellow scientists hope will lead to new treatments for things like HIV, cancer, and other illnesses.

On hand at the announcement ceremony, Goran Hansson from the Nobel panel explained their work in the context of other research going on in the exciting field.

"It follows in that line of major discoveries of how our genes function to control life. Of course there were many scientists involved in this field who made contributions but many questions, as I said in my presentation, remained. So it was quite a paradigm shift when Fire and Mello presented this paper and provided an explanation for all these questions that were raised," explained Hansson.

While both Fire and Mello knew there was the possibility of winning this year's prize, usually it is not awarded until decades have passed. Jornvall told the assembled journalists in Stockholm how the news was received.

"They were both very happy. One of them answered very quickly and looked like he realized it. The other one first lifted the telephone and then put it down again, he said."

It is believed the work of Fire and Mello will translate into many new therapies. The two will share the prize of nearly $1.4 million.