Scientists from Oxford University have uncovered clues as to how mammal genomes became riddled with viruses. The research, supported by the Wellcome Trust, reveals important information about the so-called ‘dark matter’ of the human genome.
For years scientists have been struggling with the enigma that more than 90 percent of every mammal’s genome has no known function. A part of this ‘dark matter’ of genetic material is known to harbour pieces of DNA from ancient viruses that infected our ancestors going back as far as the age of the dinosaurs.
Researchers at Oxford University, the Aaron Diamond AIDS Research Center in New York, and the Rega Institute in Belgium wanted to know how these ancient viruses got into their hosts’ genomes in such abundance.
The team searched the genomes of 38 mammals covering a large range of species: from mouse, rat and bat to human, elephant and dolphin. Genetic material from all of the residing viruses was collected and then compared using mathematical models.
The findings revealed that one particular group of viruses had lost the ability to infect new cells. Their genetic material is still able to amplify itself but the whole lifecycle of the virus is passed within a single cell: this change, they found, was followed by a dramatic proliferation of viral genetic material within the genomes.