Date: August 6, 2018
Source: University of Illinois College of
Agricultural, Consumer and Environmental Sciences
Summary:
A new study in koalas uncovers
how virulent retroviruses become harmless bits of 'junk DNA' over time.
The human genome is riddled with
endogenous retroviruses -- little pieces of degraded and generally harmless
retrovirus DNA passed down through the generations, along with our own genetic
information. Because most endogenous retroviruses have been part of our DNA for
millions of years, scientists can't explain how they went from their virulent,
disease-causing forms to the inert bits of "junk DNA" most of them
are today. A new study published today in the Proceedings of the National
Academy of Sciences looks to koalas for an answer.
"In humans, the youngest
known endogenous retrovirus groups are around 5 million years old. That makes
it very hard to tell what happened. But the koala is one of the few species
known to have an ongoing invasion of the germline by a retrovirus," says
Alfred Roca, one of the authors of the study and an associate professor in the
Department of Animal Sciences at the University of Illinois.
Like other viruses, retroviruses
first attack from the outside. They enter the body, fuse with cells to release
their contents, and insert pieces of their DNA into the genetic code of the
host, hijacking the host's DNA-replicating machinery to make more copies of
themselves.
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