Fruit flies are a "tool" to study biological processes

Five genetically identical fruit flies were produced at the lab of Dr Vett Lloyd at Dalhousie University in Halifax, Nova Scotia, Canada.

They join an expanding menagerie of creature copies that now includes sheep, mice, rats, cows, and even cats.

Fruit flies have long been a "model" to study reproductive biology and the team thinks its insects may help science understand why cloning is often flawed.

"That's pretty much the only reason why you would want to do this," Dr Lloyd told BBC News. "There are more than enough fruit flies in the world."

Failure rate

The Dalhousie fly clones were produced in a slightly different way to the method made famous with Dolly the sheep.

In that process, the genetic material of the adult animal to be copied was taken from one of its cells and injected into an emptied egg, and then coaxed into becoming a developing embryo.

For the Dalhousie flies, the donor genetic material came not from an adult cell but from an embryo cell.

It is generally thought to be easier to clone this way. Even so, it still took about 800 transfers to produce the five fly copies.

And the abnormalities that blighted many of the copying attempts echoed the problems seen in mammal cloning. Currently, many of the large animal clones that are born experience ill-health and die prematurely.

This acts as a bar to the application of cloning technology in areas that might improve the quality of agricultural livestock or produce useful drug products in animals.

'Long road'

Researchers believe the very low efficiency is due to the injected genetic material failing to properly "reprogramme" back to a true embryonic state.

Normal reproduction relies on a key process known as imprinting. This allows only specific copies of genes to be active, depending on whether they come from the male sperm or the female egg.

Live, healthy mammal clones are very difficult to produce

Many of the problems associated with cloning, it is thought, stem from the misregulation of genes that would normally have been silenced in correctly developing embryos.

The Lloyd team intends to investigate this issue with their fly clones.

Flies are relatively easy to experiment with and scientists have a good grasp of their genetics (the genome of the fruit fly Drosophila melanogaster was decoded in 2000).

"If we can see in flies where the process goes wrong and these genes are conserved in mammals then maybe you could correct it in mammal cloning - but that is a long, long way down the road," Dr Lloyd said.

The group's work has now progressed to produce a dozen clones.