Scientists rebuild part of mammoth’s genome

PARIS: In a world first, German scientists say they have reconstructed a key sequence in the genome of the woolly mammoth, enabling them to show that the extinct beast’s closest modern relative is the Asian elephant.

Reporting in Nature researchers say they devised a new technique for the feat, teasing out DNA from just 200 milligrams of bone found at a mammoths’ graveyard in the Siberian permafrost.

Their technique, called multiplex polymerase chain reaction, copied 46 chunks of sequence, which were rearranged to give a picture of the creature’s mitochondrial DNA.

The mitochondria are an internal part of a cell that is the cell’s power supply. Mitochondrial DNA is handed down through the maternal line, and is a relatively stable genetic sequence — it changes little from generation to generation, and at a measurable rhythm.

This makes mitochondrial DNA a useful “molecular clock” that can be wound backwards into time, to see how a species evolved.

By comparing the sequence with that of modern animals, scientists can spot when and where species diverged from their common ancestor.

In this case, the closest relative today to Mammuthus primigenius is the Asian elephant rather than the African elephant, the researchers say. The difference, though, is not great.

African elephants branched away from the mammoth’s evolutionary tree around six million years ago. Asian elephants followed suit around only 440,000 years later. That timeline of divergence is close to chimps and humans.

Genome sequence reconstructed: German researchers copied chunks of DNA sequence, which were rearranged to give a picture of the DNA of the mitochondria, the part of the cell that generates power. Comparing the Mitochondria’s sequence, researchers found that the mammoth is more closely related to the Asian elephant and not the African one.

By gently amplifying the DNA, the researchers were able to get 5,000 base pairs, even though the sample was degraded.