Scientists in the past decade have discovered that remnants of ancient germ line infections called human endogenous retroviruses make up a substantial part of the human genome. Once thought to be merely "junk" DNA and inactive, many of these elements, in fact, perform functions in human cells.

Now, a new study by John McDonald of the University of Georgia and King Jordan at the National Center for Biotechnology Information at the National Institutes of Health, suggests for the first time that a burst of transpositional activity occurred at the same time humans and chimps are believed to have diverged from a common ancestor - 6 million years ago. These new results implicate retroelements, a particular type of transposable elements that are abundant in the human genome, in the actual shift from more rudimentary primates to modern human beings. The research was just published in the journal Genome Letters.

"There is a growing body of evidence that transposable elements have contributed to the evolution of genome structure and function in many species," said McDonald, a molecular evolutionist and head of the genetics department at UGA. "Our results suggest that a bust of transposable element activity may well have contributed to the genetic changes that led to the emergence of the human species." Jordan received his doctoral degree at UGA working with McDonald.

There has been a molecular arms race going on between transposable elements and their host genomes for millions of years. Host genomes are continually evolving new regulatory mechanisms to silence the mutagenic effects associated with the replication of these elements which, in turn, place selective pressure on the elements to evolve mechanisms to escape these controls. The result is an internal drive mechanism to increase biological complexity.

Just as new technologies generated by the military arms races between rival countries get spun off and used for non-military purposes, s
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Contact: Kim Carlyle
kosborne@uga.edu
706-583-0913
University of Georgia
1-Aug-2002

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