Sequence and rewind: Scientists are racing to clone the extinct woolly mammoth and other prehistoric beasts, perhaps one day creating a real life 'prehistoric zoo'.

Credit: AFP

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Freezing preserves biological molecules that would otherwise swiftly degrade after death. A dead cell doesn't possess any of the usual machinery required to repair DNA damage, and long chains of DNA disintegrate into smaller fragments while some bases (A, T, C, and G - the molecules that make up the genetic code) mutate into others.

Cells with DNA in fragments only 100 to 200 base pairs long cannot be used for cloning as they are not able to grow, divide and create proteins in the same way as cells with intact DNA. However, if an animal is frozen within days of dying - and remains frozen - the process of degradation is slowed or even halted.

Iritani hoped, at first, to find frozen sperm from a mammoth. The sperm would be used to impregnate a modern-day elephant, creating a hybrid species. As more mammoths are born the elephant genes could eventually be bred out. Frozen sperm, though, would be an incredibly lucky find. As an insurance policy, any tissue samples found are stored, as the team firmly believes that scientists will find a way to piece together the fragmented DNA.

Creating a real-life Pleistocene Park may sound like a rather far-fetched idea, but it is already under way. A Russian scientist has been cultivating a suitable location in Siberia for more than a decade. He hopes to recreate the entire landscape and ecosystem of 10,000 years ago - perfect for recently resurrected woolly mammoths. In total, the park would be about twice the twice of England.

While mammoth experts scoff at such an idea, Iritani has already proven he knows what he is doing. Six months before announcing plans for Pleistocene Park, Iritani's team successfully transplanted a spinach gene into a pig. The result was an animal that creates less fatty acid and produces a healthier pork product. Only time will tell if he can be successful in his new, and far more ambitious project.

The woolly mammoth is a popular target among many cloning experts. The disgraced South Korean scientist Hwang Woo-Suk (see Cosmos, Issue 8, p64), who successfully cloned Snuppy the dog, had obtained woolly mammoth tissue for cloning purposes. In another admission of breached ethics, Hwang recently admitted in court that his team obtained the samples by paying the Russian Mafia.

Other extinct animals on cloning experts' to-do list include the Tasmanian tiger and the Spanish mountain goat, both of which were driven extinct by human forces. It is even conceivable that animals as long-gone as dinosaurs will one day make the list, despite not being preserved immediately after death.

Most twentieth century scientists insist that Jurassic Park is still science fiction, while others readily admit the methods described in the movie thriller could actually be one future possibility. In Jurassic Park, dinosaur DNA was obtained from the blood in the stomachs of insects entombed in amber. The sequences vital for making the right dinosaur were targeted and spliced into host DNA from modern amphibians, and the dinosaurs were grown in artificial eggs.

The struggle to recover ancient DNA has had a tumultuous history in life, as well as in the movies. Because DNA degrades over time, it was long considered impossible to retrieve anything useful. False reports in 1994 of a DNA find in an 80-million-year-old dinosaur bone was only the first in a series of high-profile failures as researches tried to obtain DNA of ancient animals.

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