Washington: Scientists claim to have found a key genetic indicator to predict an individual`s life span by measuring the length of tiny pieces of DNA called telomeres.
Telomeres are stretches of repetitive DNA sequence found at the ends of chromosomes that gradually wear away as we age.
Now, a team at the Glasgow University in the UK found that the length of these caps measured early in life can help predict how long can one live, LiveScience reported.
Using 99 zebra finches, a small bird also popular as a pet, the team measured the lengths of the telomeres, found in the birds` red blood cells over the course of their lives.
They discovered the length of the telomeres at the first measurement, made 25 days after the birds hatched, was the strongest predictor of how long the birds actually lived.
In addition, the birds with the longest telomeres early in life, and throughout the study, were the ones most likely to live into old age, up to 8.7 years old -- a "ripe old age" for a finch, said study author Britt Heidinger, a postdoctoral researcher at the University of Glasgow.
For relatively long-lived vertebrates, like zebra finches and humans, ageing and telomere loss appear to go hand-in-hand.
And while it seems reasonable that telomere length early on could predict life span in humans too, it`s not yet certain, since no study has been done in humans, Heidinger said.
"This is one piece that we have measured, there are many, many things that contribute to ageing in individuals," he said.
"It could be multifaceted and there could be many different causes, we are not saying (loss of) telomeres are the only cause of death."
Chromosomes are threadlike strands of protein and DNA, which contain the instructions to make a living thing. Each of our cells contains chromosomes, capped by telomeres, and when our cells divide -- a necessary part of maintenance and growth of our bodies -- these chromosomes must be duplicated.
In the study, published in the journal Proceedings of the National Academy of Sciences, the birds were allowed to live out their natural lives, with blood samples taken when they were 25 days old, then 1 year old, and periodically afterward.
The length of telomeres, which serve as markers for the ends of the chromosomes, measured at other times during the birds` lives did not have the same strong correlation to life span as the initial measurement.
The researchers did not track the birds` eventual cause of death, but they know these did not include accidents, predators, starvation or infection.
Many other factors -- damage elsewhere in the DNA, damage to biologically important molecules, reduced capacity to replace lost cells, and so on -- are also implicated in
The loss of telomeres may ultimately contribute to death by causing body systems to fail, but which systems and when are likely to vary, resulting in different causes of death for
different individuals, the researchers said.