An international research team reported on Monday that it has mapped part of the genome of the woolly mammoth, a huge relative of today's elephant extinct for about 10,000 years.

Using a combination of novel techniques, the researchers have sequenced a chunk of ancient DNA belonging to remains of a woolly mammoth and "fellow travelers," including a sample of the bacteria, fungi, viruses and plants that lived at the same time as the mammoth.

The remains of the mammoth, which lived in Siberia about 28,000 years ago, were well preserved in the permafrost, the researchers from Canada and the United States said in the Dec. 22 online edition of the journal Science.

This breakthrough allows for the first time a comparison of this ancient species with today's African and Indian elephants at the level of nuclear genome, said the team led by Hendrik Poinar, a professor at the McMaster University in Canada.

The techniques used by the researchers produced an impressive amount of nuclear DNA, they said. The sequencing feat extracted nuclear DNA from the mammoth's jawbone, concentrating the DNA into a single-molecule serving size that was enclosed in a lipid bubble before it was amplified and sequenced by a relatively new technique called pyrosequencing.

The researchers identified that 13 million base pairs, nearly half of the total base pairs in the bubble, as belonging to the mammoth, which are very similar to the African elephant genome.

"Thanks to exceptional sample preservation and use of a novel emulsion polymerase chain reaction and pyrosequencing technique, 13 million base pairs (45.4 percent) of the sequencing reads were identified as mammoth DNA," said the researchers.

"Sequence identity between our data and African elephant ( Loxodonta africana) was 98.55 percent, consistent with a paleontologically based divergence date of 5 to 6 million years," they wrote in the paper.

This was a "surprising finding," according to the researchers, as it demonstrated that the analyzed material was frozen for so many years. The findings indicate that any organism that has been trapped in frozen ice or a permafrost environment for up to 1 million years will be "an open book," they said.

"The ability to obtain this level of genetic information from extinct species makes it possible to consider detailed analysis of functional genes, and fine scale refinement of mutation rates."

On the same day, another team of the Max Planck Institute in Germany also reported their achievement in sequencing mammoth genome. The team studied the DNA of mammoth's mitochondrion, which located outside the nucleus of a cell.

Differing from the conclusion of their Canadian-US colleagues, the German researchers reported in the journal Nature that the woolly mammoth was more closely related to the Asian than the African elephant, but that the divergence between the three occurred over a short time.

"Our phylogenetic analyses show that the mammoth was more closely related to the Asian than to the African elephant. However, the divergence of mammoth, African and Asian elephants occurred over a short time, corresponding to only about 7 percent of the total length of the phylogenetic tree for the three evolutionary lineages, " they said.

Source: Xinhua