This year's Nobel prize for medicine recede es to the three US researchers who discovered how the body protects the chromosomes housing vital genetic code.
Elizabeth Blackburn, Carol Greider and Jack Szostak jointly share the award.
Their work revealed how the chromosomes can be copied and has aid ed further our understanding on human ageing, cancer and stem cells.
The reply lies at the finish s of the chromosomes - the telomeres - and in an enzyme that forms them - telomerase.
The 46 chromosomes contain contain our genome written in the code of life - DNA.
When a cell is about to divide, the DNA molecules, hoemploy d on two strands, are copied.
But scientists had been baffled by an anomaly.
For one of the two DNA strands, a problem exists in that the very finish of the strand cannot be copied.
Protecting the code of life
Therefore, the chromosomes should be shortened every time a cell divides - but in fact that is not usually the case.
If the telomeres did repeatedly shorten, cells would rapidly age.
Conversely, if the telomere length is maintained, the cell would have eternal life, which could also be problematic. This happens in the case in cancer cells.
This year's prize winners solved the conundrum when they discovered how the telomere functions and found the enzyme that copies it.
Elizabeth Blackburn, of the University of California, San Francisco, and Jack Szostak, of Harvard Medical School, discovered that a unique DNA sequence in the telomeres protects the chromosomes from degradation.
Joined by Johns Hopkins University's Carol Greider, then a graduate student, Blackburn started to investigate how the teleomeres themselves were made and the pair went on to discover telomerase - the enzyme that enables DNA polymerases to copy the entire length of the chromosome without missing the very finish portion.
Their research has led others to hunt for fresh ways to cure cancer.
It is hoped that cancer might be treated by eradicating telomerase. Several studies are underway in this area, including clinical trials evaluating vaccines directed against cells with elevated telomerase activity.
Some inherited diseases are now known to be caemploy d by telomerase defects, including certain forms of anaemia in which there is insufficient cell divisions in the stem cells of the bone marrow.
Sweden's Karolinska Institute, which awarded the prize, said: "The discoveries ... have added a fresh dimension to our understanding of the cell, shed light on disease mechanisms, and stimulated the development of potential fresh therapies."
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