Australian-American-British trio share Nobel for medicine

Australian-born Elizabeth Blackburn along with British-born Jack Szostak and American Carol Greider, have won the 2009 Nobel Prize for medicine or physiology.

An announcement by the Nobel Prize committee said this year's Nobel Prize for physiology or medicine has been awarded to the three scientists for solving a major problem in biology - how chromosomes can be copied in a complete way during cell divisions and how they are protected against degradation.

The Nobel laureates have shown that the solution is to be found in the ends of the chromosomes - the telomeres - and in an enzyme that forms them - telomerase, the announcement said.

"The long, thread-like DNA molecules that carry our genes are packed into chromosomes, the telomeres being the caps on their ends. Elizabeth Blackburn and Jack Szostak discovered that a unique DNA sequence in the telomeres protects the chromosomes from degradation. Carol Greider and Elizabeth 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 release said.

"If the telomeres are shortened, cells age. Conversely, if telomerase activity is high, telomere length is maintained, and cellular senescence is delayed. This is the case in cancer cells, which can be considered to have eternal life. Certain inherited diseases, in contrast, are characterised by a defective telomerase, resulting in damaged cells," the release said, adding, "The award of the Nobel Prize recognises the discovery of a fundamental mechanism in the cell, a discovery that has stimulated the development of new therapeutic strategies.

The release said their discovery of how the so-called telomeres prevent the chromosomes from attaching to each other and how the enzyme copies it has solved the problems of how telomeres operate and how when a cell is about to divide, the DNA molecules, which contain the four bases that form the genetic code, are copied, base by base, by DNA polymerase enzymes.