Mammoth DNA half-mapped
The sequence comes from DNA in hair snipped from two woolly mammoths whose bodies have been preserved in Siberian permafrost for tens of thousands of years. -AFP
PARIS - SCIENTISTS said on Wednesday they had reconstructed around half of the genome of the woolly mammoth, a species that became extinct at the end of the last Ice Age some 11,000 years ago.
The sequence comes from DNA in hair snipped from two woolly mammoths whose bodies have been preserved in Siberian permafrost for tens of thousands of years, they reported in the British-based weekly journal Nature.
Important gaps in the picture remain, but even so, enough data is there to make a comparison between the woolly mammoth (Mammuthus primigenius) and its closest living relative, the elephant, they said.
The two species are so similar that their DNA differs by just 0.6 per cent, or about half the differences between humans and chimps.
The team, led by Dr Stephan Schuster of Pennsylvania State University, notched up a first breakthrough last year by using mammoth hair to extract mitochondrial DNA, genetic material that is inherited from the female line.
The latest work focuses on nuclear DNA, or chromosome-bearing strands that have the most important protein-making software.
'We're sequencing random fragments and believe we have 50 per cent of the genome. We don't yet know the full size of the genome,' co-author Webb Miller told AFP in a phone interview.
The hair technique marks a giant's step forward compared to the previous method, which consisted of teasing DNA out from bone marrow in the remains of frozen marrow.
DNA of this kind can be badly damaged by bouts of freeze-thaw over the millennia, enabling water and bacteria to enter through porous bones.
But the keratin sheath of hair provided a surprisingly good shield for the DNA inside, said Dr Miller.
The two mammoths from which the hair shafts were taken died around 20,000 years and 50,000 years ago respectively.
In addition to the new source for gene sequencing, the scientists have harnessed new technology that can unravel DNA code in a fraction of the time it took a few years ago.
Rebuilding the mammoth's genetic code has fired speculation that scientists may one day revive this species and other Ice Age beasts on the lines of the Hollywood movie 'Jurassic Park'. These creatures became extinct relatively recently, offering the possibility of recovering scraps of DNA from bodies that have been preserved in bitter sub-freezing chill.
Dr Miller said it should one day be theoretically possible to replicate a mammoth - or rather, a mammoth-like animal - by taking the elephant's genome, stripping out the code that is specific to the elephant and replace it with code specific to the mammoth.
The new code would be fused into an elephant's egg, replacing its programming nucleus, and then be transplanted into a female elephant.
But, he said, such an endeavour was fraught with technical hurdles and would need lots of money.
If the interest to achieve it was there, the first step would be to be compare the genome of the elephant - its publication is expected next year - with a complete error-free genome of the mammoth.
'What will be possible some day in the future is to synthetically make all the substitutions within the elephant sequence,' he said.
'Doing that, you're going to need to know the sequence. The work that we did represents a large step in that direction. We need to get not only the other 50 per cent of the genome, but we need to sequence each base pair many times to make sure there are no sequencing errors.'
Dr Miller argued that the fast-track methods for gene sequencing and analysing could be of greater use in saving species today rather than reviving species of the past.
The team was poring the genome of the Australian marsupial called Tasmanian devil, whose numbers have been ravaged by cancerous facial tumours.
'We're looking at the genome to make suggestions to guide the breeding programme, saying 'a version of gene X is known to be associated with resistance to cancers, so you should save this individual and that individual,' but also retain genetic diversity,' he said.
Why the woolly mammoth died out is a mystery in itself. Some scenarios blame climate change that destroyed its sources of food; others say it was wiped out by human hunters. -- AFP
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