Three scientists have been jointly awarded the Nobel prize for medicine for discovering how the body protects the chromosomes housing vital genetic code.

The Nobel Assembly at Karolinska Institute today said the Nobel Prize in Physiology or Medicine 2009 would be jointly awarded to Elizabeth Blackburn, Carol Greider and Jack Szostak for the discovery of "how chromosomes are protected by telomeres and the enzyme telomerase".

In a statement from the assembly, which is made up of 50 professors, said the three scientists were awarded the prize because they had "solved a major problem in biology: how the chromosomes can be copied in a complete way during cell divisions and how they are protected against degradation".

The Laureates found the solution to this problem was to be found in the ends of the chromosomes – the telomeres – and an enzyme that forms them – telomerase.

Ms Blackburn and Mr Szostak discovered that a unique DNA sequence in the telomeres protects the chromosomes from degradation.

Ms Greider and Ms Blackburn identified telomerase, the enzyme that makes telomere DNA.

These discoveries explained how the ends of the chromosomes are protected by the telomeres and that they are built by telomerase.

The judges of the prize said: "These discoveries had a major impact within the scientific community.

"Many scientists speculated that telomere shortening could be the reason for ageing, not only in the individual cells but also in the organism as a whole. But the ageing process has turned out to be complex and it is now thought to depend on several different factors, the telomere being one of them. Research in this area remains intense."

They added that the discoveries by Ms Blackburn, Ms Greider and Mr 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.

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