Screening for the ancient polar bear mitochondrial genome reveals low integration of mitochondrial pseudogenes () in bears.

Phylogenetic analyses of nuclear and mitochondrial genomes indicate that polar bears captured the brown bear mitochondrial genome 160,000 years ago, leading to an extinction of the original polar bear mitochondrial genome. However, mitochondrial DNA occasionally integrates into the nuclear genome, forming pseudogenes called (nuclear mitochondrial integrations). Screening the polar bear genome identified only 13 . Genomic analyses of two additional ursine bears and giant panda indicate that all except one of the discovered entered the bear lineage at least 14 million years ago. However, short read genome assemblies might lead to an under-representation of or other repetitive sequences. Our findings suggest low integration rates of in bears and a loss of the original polar bear mitochondrial genome.