Clues from Koalas

Alongside protein-coding genes, the human genome contains many non-coding sequences, so-called 'junk DNA', including an estimated 8% of our DNA derived from retroviruses. These viruses replicate by inserting their DNA into their hosts’ genomes; if inserted into the DNA of germ cells, giving rise to ovules and sperm, they can be passed on to future generations, eventually losing their viral function. Retroviral insertions in our genome are very ancient, but a more recent, ongoing invasion has been discovered in koalas (pictured), allowing us to study this process in action. Research shows that shuffling genetic material during DNA replication, between koala retrovirus (KoRV) and more ancient retroviral elements in the genome, can quickly disable KoRV. Known as recombination, this mechanism is likely to be a key early step towards retroviral integration. As researchers continue to monitor koala retroviruses, these beloved Australian icons may help us piece together our own genome’s history.

Written by Emmanuelle Briolat

Emmanuelle Briolat

Writer

A researcher specialising in visual signals in Lepidoptera, camouflage and the effects of light pollution, Emmanuelle’s writing covers a range of topics, from biomedical research to children’s books about moth defences.

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• Image by Emmanuelle Briolat
• Research from the Department of Wildlife Diseases, Leibniz Institute for Zoo and Wildlife Research, Berlin, Germany; Australian Museum Research Institute; Department of Animal Sciences, University of Illinois at Urbana–Champaign
• Image copyright held by the photographer
• Research published in PNAS, August 2018