Stockholm: Americans Elizabeth H. Blackburn, Carol W. Greider and Jack W. Szostak won the 2009 Nobel Prize in medicine on Monday for discovering a key mechanism in the genetic operations of cells, an insight that has inspired new lines of research into cancer.

The trio solved the mystery of how chromosomes, the rod-like structures that carry DNA, protect themselves from degrading when cells divide.

Chromosome research: A file photo of US biologists Elizabeth H. Blackburn (left) and Carol W. Greider. The two, along with Jack W. Szostak, have won the prize for discovering a key genetic mechanism. Michael Probst / AP

Blackburn and Greider discovered the enzyme that builds telomeres—telomerase—and the mechanism by which it adds DNA to the tips of chromosomes to replace genetic material that has eroded away.

The prize winners’ work set the stage for research suggesting that cancer cells use telomerase to sustain their uncontrolled growth. Scientists are studying whether drugs that block the enzyme can fight the disease. In addition, scientists believe that the DNA erosion the enzyme repairs might play a role in some illnesses.

“The discoveries by Blackburn, Greider and Szostak have added a new dimension to our understanding of the cell, shed light on disease mechanisms, and stimulated the development of potential new therapies," the prize committee said in its citation.

It was the first time that two women have been among the winners of the medicine prize, committee members said.

Blackburn, who holds US and Australian citizenship, is a professor of biology and physiology at the University of California, San Francisco. Greider is a professor in the department of molecular biology and genetics at Johns Hopkins University School of Medicine in Baltimore.

“It’s really very thrilling, it’s something you can’t expect," Greider, 48, said over the phone.

People might make predictions of who might win, but one never expects it, she said, adding that, “It’s like the Monty Python sketch, ‘Nobody expects the Spanish Inquisition!"’

The award includes a 10 million kronor (Rs6.65 crore) purse divided among the winners, a diploma and an invitation to the prize ceremonies in Stockholm on 10 December.

The researchers have already won a series of medical honours for their enzyme research. In 2006, they shared the Lasker prize for basic medical research, often dubbed “America’s Nobel".