Genome Extracted from Ancient Polar Bear Fossil

Genetic analysis of the DNA in a polar bear jawbone has finally yielded the first genome of the polar animal. The fossil, which was recovered in 2004 from Svalbard, Norway, belongs to a specimen that lived between 110,000 and 130,000 years ago, and researchers say that it provided them with definite proof that this species, Ursus maritimus, derived from its nearest common relative, Ursus arctos, or the brown bear. This fossil is extremely valuable to science because polar bears don't usually live fossils behind. They live on the ice, where very few natural traps to preserve them exist, Nature News reports.

In other types of climates, watering holes, tar pits, mud fields and swamps provide ideal conditions for capturing an animal, and preserving it over millions of years, but ice caps do not have this ability. Therefore, identifying this particular polar bear remnant was extremely important. The fact that enough DNA to base a genome on could also be recovered adds even more weight to the new study. The work was based on mitochondrial DNA, which researcher Charlotte Lindqvist obtained by drilling into the jawbone. In addition to the bear bone, the team also found a canine tooth at the same location.

Lindqvist, the leader of the new investigation, is a molecular biologist based at the University of Buffalo in New York. She conducted the investigation while at the University of Oslo Natural History Museum. The expert explains that mitochondria are organelles in all animal cells that play a huge role in providing energy for other cellular components. They are also commonly referred to as the power plant of the cell. They possess their own kind of DNA, which is more abundant inside the cell than nuclear DNA. In order to sequence a polar bear genome based solely on these samples, Lindqvist worked with Pennsylvania State University molecular biologist Stephan Schuster.

The group found that some of the DNA strands in their samples were broken apart, and degraded, as one would expect from such an old source. But the experts say that the damage could have been a lot worse, given the age of the jawbone. They explain that the cold and dry conditions at the location where the jawbone was discovered contributed to keeping the DNA inside in better shape than it would have otherwise been in. “Many researchers would have thought it impossible to retrieve DNA from a bone specimen as old as this polar bear. The result is a true eye opener – it gives hope to future projects trying to genome sequence truly old bone specimens,” concludes University of Copenhagen evolutionary biologist Eske Willerslev.