Researchers have identified genes that perform a key role in the ageing process, boosting efforts of scientists aiming to possibly extend the natural human life span.

The study appearing in the journal Genome Research looked for genes that control the ageing process in two primitive organisms, yeast cells and nematode worms -- separated by 1.5 billion years of evolution.

By mapping how different genes play their role in the ageing process, researchers hope to identify ways to treat old age diseases and possibly slow down the process itself.

Brian Kennedy at the University of Washington in Seattle and his team found that of the 276 genes known to affect ageing in nematode worms, only 25 were also present in yeast. At least 15 of these have similar versions in humans.

"Nematodes and humans are more similar to each other on an evolutionary scale than nematodes and yeast," said Erica Smith, a leading author of the study.

"We reasoned that if a particular gene modulates ageing in both yeast and nematodes, there is a good chance that gene plays a similar role in people," Smith was quoted as saying by the British daily The Guardian on Thursday.

Previous studies have illustrated that a major cut in calories in an organism's diet can extend its life period, though often at the expense of fertility, the report said.

It said if scientists can find out how age-related genes are affected by an extremely low-calorie diet, they may be able to replicate the effect. "What we would like to eventually do is mimic the effects of dietary restriction with a drug," said Matt Kaeberlein, a co-author on the study.