Three scientists have shared this year's Nobel Prize for Medicine for their pioneering work in understanding how chromosomes - the microscopic filaments containing a cell's genetic material - are able to divide repeatedly without falling apart.
They discovered how structures called telomeres, at the tips of the chromosomes, allow the cell's long molecules of DNA to replicate without getting shorter. They also worked out how telomeres are able to replenish and prevent premature ageing of the cell.
The work has revolutionised cancer research and the study of tissue ageing.
It is now known that telomeres, and the enzyme telomerase that helps to make them grow again after they have been shortened in each cell division, are central to the process by which a cell stops dividing and dies, or continues to divide and forms a cancerous tumour.
All three scientists work in the United States. Australian-born Elizabeth Blackburn, British-born Jack Szostak and United States-born Carol Greider share 10 million Swedish kronor ($1.9 million), which was awarded by the Nobel Assembly at the Karolinska Institute in Stockholm.
"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 Karolinska Institute said yesterday.
Greider, 48, from Johns Hopkins University in Baltimore, said that the early work she carried out with colleagues in the 1980s was driven by scientific curiosity rather than hopes of a practical use.
"We had no idea when we started this work that telomerase would be involved in cancer, but were simply curious about how chromosomes stayed intact," she said.
"Our approach shows that while you can do research that tries to answer specific questions about a disease, you can also follow your nose."
Telomeres have been likened to the plastic tips of bootlaces that stop them from fraying.
They bind to the end of the chromosomes, preventing them from fragmenting during cell division.
Blackburn, from the University of California, San Francisco, and Szostak, from Harvard Medical School, showed that specific sequences of DNA building blocks within the telomeres of one species of microbe can be placed on the ends of artificial chromosomes to protect them from disintegrating when the chromosomes are inserted into the cells of an unrelated species.