Fruit flies that had the human gene transplanted into their genetic makeup lived 40 per cent longer than the ones without it.

The gene, superoxid dismutase (SOD1) present in every human cell, checks the free radicals and prevents the damage they cause to cells, reports Tony Parkes of Guelph University, Ontario, along with colleagues from Toronto University.

Parke's team believes that the gene's most important function is to protect the nervous system. On the other hand, tiny changes in the gene appear to increase vulnerability towards several nervous disorders. A mutant version of SOD1 causes a form of sclerosis.

Scientists hope that they will be able to fight neuro-degenerative diseases by transplanting healthy copies of SOD1 genes or by developing medication based on their findings.