Tuesday September 6, 2005

Guardian Unlimited

The thylacine, a wolf-like creature with a backwards-facing pouch and jaws the size of a shelf bracket, was the biggest meat-eating marsupial.

Since the last living specimen, named Benjamin, died in Hobart zoo on the night of September 6 1936, it has become a conservation icon.

Scientists at the Australian Museum, in Sydney, first proposed bringing the thylacine back to life in 1999, but the plans were abandoned earlier this year when researchers said the DNA they had recovered was too poor in quality.

However, the museum's former director told Guardian Unlimited that a team of Australian and US researchers were restarting the project and hoped to use new techniques that could lead to the sequencing of the entire thylacine genome.

Professor Mike Archer, now dean of the University of New South Wales, said DNA recovered from bones and teeth in Australian museum collections had proved to be promising.

"We've undoubtedly got the whole of the genome in the recovered DNA, although there's thousands more genes than we've been able to recover so far," he said.

"We've managed to sequence nuclear and mitochondrial genes, but there's still much less than 1% of the information we need."

In 2002, scientists succeeded in replicating large quantities of thylacine genes - a crucial first step towards cloning the animal.

Last year, Mr Archer held discussions on the project with the US genome expert Craig Venter, whose DNA sequencing techniques spurred the race to decode the human genome in 1999.

However, there are still enormous hurdles to be overcome and many geneticists doubt whether the project is feasible.

Producing the chromosomes necessary to clone an organism requires the production of multiple copies of entire DNA strands - something the Australian researchers are a long way from accomplishing.

In addition, the nuclear transfer technique used for cloning requires whole cell nuclei to be present, rather than simply the library of information that sequencing the thylacine's DNA will produce.

But Mr Archer said one cited problem - the difficulty of finding a surrogate parent for the thylacine - need not hold up the project.

He said several surviving marsupials were genetically close enough to the thylacine to act as wombs. "For a Tasmanian devil to give birth to a thylacine wouldn't be a trouble at all," he said.

He explained that the difference in size between the two animals would not pose a problem because marsupials are born in an undeveloped state.

Red kangaroos, which grow to stand more than 6ft tall, are just a few centimetres long at birth.

Ironically, the decline of the thylacine in the wild was accelerated by the rush of museums and zoos to collect specimens in the early 20th century.

Wildlife officials still receive regular reports of thylacine sightings from remote areas of Tasmania, although most are quickly explained as misidentifications.