- Scientists have extracted and decoded the DNA of a cave
bear that died 40,000 years ago.
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- They plan to unravel the DNA of other extinct species,
including our closest ancient relatives, the Neanderthals.
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- But they say the idea of obtaining DNA from dinosaurs,
depicted in the film Jurassic Park, remains science fiction.
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- It is highly unlikely that viable genetic material will
ever be recovered from fossils that are hundreds of millions of years old.
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- But the scientists hope to be able to sequence the DNA
of ancient humans, which lived at the same time as cave bears, raising
the prospect of perhaps one day being able to "build" a Neanderthal
from their genetic blueprint.
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- Jurassic Park
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- "In hundreds or thousands of years from now, we
may have advanced our technology so we can create creatures from DNA sequence
information," Dr Eddy Rubin, director of the US Department of Energy
Joint Genome Institute in Walnut Creek, California, told the BBC News website.
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- "I don't think we can extract DNA from dinosaurs;
I think they are too old. As for creating Jurassic Park, I think that remains
science fiction."
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- The scientists extracted DNA from the tooth and bones
of cave bears found at two sites in Austria.
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- The cave bear was once common in Europe but died out
about 10,000 years ago, when the forests shrank at the end of the last
Ice Age.
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- Dr Rubin's team analysed the extinct bear's DNA using
powerful computing technology developed during the human genome project.
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- This approach has been hampered in the past by the fact
that ancient DNA is contaminated with genetic material from bacteria and
people who have handled the ancient remains.
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- Sifting out the ancient DNA from this genetic soup is
like looking for a needle in a haystack.
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- But because we now know the genetic sequences of many
organisms - including numerous microbes, the human, and animals such as
the dog - the researchers were able to isolate the sequences they were
interested in.
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- In the case of the cave bear, they used the sequence
of the dog, which exists in public databases, and the DNA of modern bears,
as a "magnet".
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- Dr Rubin said it served as a "proof of principle"
that the method works.
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- They are now turning their attention to the Neanderthals,
the closest ancient relatives of modern humans, who lived around the same
time as the bears.
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- "I think it will work," he said. "It is
just a matter of time."
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- Mitochondrial DNA
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- Most fossils are of no use to scientists hunting ancient
biomolecules. It is only in those specimens where some sub-fossil material
- tissues that have not been fully mineralised - still exists that researchers
can hope to retrieve some genetic information.
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- And in the last few years, a number of labs have developed
the expertise to extract fragments of DNA from animals that died out tens
of thousands of years ago.
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- Most of these samples, though, have been from mitochondria,
the structures in the cell that produce energy and have their own genetic
material.
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- While this can provide valuable information about the
evolutionary history of a species, it is the DNA within the nucleus, the
nuclear or genomic DNA, which contains the bulk of an animal's genetic
information, including the secrets of how modern animals differ from their
ancestors.
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- Dr Dan Bradley, an expert on ancient DNA at Trinity College,
Dublin, Ireland, said the research was "very encouraging".
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- "It has been very difficult thus far to get anything
other than mitochondrial DNA from ancient material," he said.
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- "That is only a very small part of our DNA with
limited interest."
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- The research is reported in the journal Science.
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- © BBC MMV
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- http://news.bbc.co.uk/1/hi/sci/tech/4602739.stm
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