Chromosomes have telomeres at the end of each strand
There is a clear link between living to 100 and inheriting a hyperactive version of an enzyme that prevents cells from ageing, researchers say.
Scientists from the Albert Einstein College of Medicine in the US say centenarian Ashkenazi Jews have this mutant gene.
They found that 86 very old people and their children had higher levels of telomerase which protects the DNA.
They say it may be possible to produce drugs that stimulate the enzyme.
Writing in the Proceedings of the National Academy of Sciences, the team say they studied the Ashkenazi Jewish community because they are closely related so it is easier to identify disease causing genetic differences.
They took blood samples from 86 very old, but generally healthy, people with an average age of 97; 175 of their offspring; and 93 other people who were the offspring of parents who had lived a normal lifespan and could therefore make up a control group, with which the results could be compared.
Role of telomeres
Telomeres are relatively short sections of specialized DNA that sit at the ends of all our chromosomes.
They have been compared to the plastic tips at the ends of shoelaces that prevent the laces from unravelling.
Each time a cell divides, its telomeres shorten and the cell becomes more susceptible to dying.
The importance of telomeres was recognised last month when three scientists received the 2009 Nobel Prize in Physiology and Medicine for determining the structure of telomeres and discovering how they protect chromosomes from degrading.
Telomerase can repair the telomeres, preventing them from shrinking.
The team at Einstein found that the centenarians and their offspring had higher levels of telomerase and significantly longer telomeres than the unrelated people in the control group and that the trait was strongly heritable.
The scientists had previously shown that individuals in Ashkenazi families with exceptional longevity have generally been spared major age-related diseases, like heart disease and diabetes.
The centenarians in this study had a lower average body mass index than the controls and higher levels of good (HDL) cholesterol.
Yousin Suh, associate professor of medicine and genetics at Einstein and a lead author on the paper, said: "Our findings suggest that telomere length and variants of telomerase genes combine to help people live very long lives, perhaps by protecting them from the diseases of old age.
"We're now trying to understand the mechanism by which these genetic variants of telomerase maintain telomere length in centenarians.
"It may be possible to develop drugs that mimic the telomerase that our centenarians have been blessed with."
Professor Tim Spector, from King's College London, who has been researching telomeres and ageing, said it was an interesting finding but it may not apply to other populations and further research was needed.
He said: "There may be a downside to the plan of boosting the repair processes of DNA because giving the cells more chances to divide may increase the chances of damaging mutations developing and causing cancer.
"Most scientists agree that there is evidence that people with long telomeres have less age-related diseases and this study does suggest that could be one reason why they are living longer."