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Archive - Jul 27, 2015

Much of Polar Bear Y-Chromosome Sequence Is Identified; Study Shows That Two Male Lineages Diverged Over 100,000 Years Ago

For the first time, a team of scientists, led by Professor Axel Janke of the Senckenberg Research Center for Biodiversity and Climate in Franfurt, Germany, has reconstructed part of the male chromosome in polar bears (Ursus maritimus). The scientists were able to assign 1.9 million base pairs specifically to the polar bear Y chromosome. In their study, published online on May 27, 2015 in an open-access article in “Genome Biology and Evolution,” they show that more than 100,000 years ago, the male polar bear lineages split and developed in two separate genetic groups. The article is titled “Genome-Wide Search Identifies 1.9 Megabases from the Polar Bear Y Chromosome for Evolutionary Analyses.” The polar bear is the world’s largest land-dwelling predator and is hard to miss. Nevertheless, it is difficult to study the evolution of this Arctic resident. Polar bears live and die on the frozen sea, and their remains are seldom found. “In order to gain insights into the evolutionary development of Ursus maritimus, we use genetics instead of fossils,” explains Professor Janke. For the first time, the evolutionary geneticist and his Ph.D. student Tobias Bidon, have reconstructed large parts of the polar bear Y chromosome. “In this age of biological revolution, it is possible to sequence the entire genome of an organism rather quickly and cost-effectively,” says Dr. Janke. However, to date, such comprehensive genome projects have mostly been limited to female animals, neglecting the males’ special chromosome – the Y chromosome. Mr. Bidon commented that “this is quite surprising, because the Y chromosome is an important part of the mammalian genome. It is the only genetic material that is passed on from male to male, thereby offering unique insights into the evolutionary history and population dynamics.”