A GENETIC arms race within ourselves has helped to shape human evolution, according to new research.
Scientists have discovered evidence of a hidden war between mobile DNA sequences known as "jumping genes" and other "repressor" genes that try to keep them under control.
Over evolutionary time, the jumping genes have developed mutations that allow them occasionally to escape their repressors.
This in turn has driven the evolution of new repressor genes, triggering more jumping gene "resistance".
The findings, published in the online edition of Nature journal, indicate that repressor genes originally designed to shut down jumping genes have been co-opted to regulate other parts of the genome. They have driven the evolution of complex networks that orchestrate the activity of our genes.
US lead scientist Sofie Salama, from the University of California at Santa Cruz, said: "We have basically the same 20,000 protein-coding genes as a frog, yet our genome is much more complicated, with more layers of gene regulation. This study helps explain how that came about."
Jumping genes, or retrotransposons, are thought to be remnants of ancient viruses that infected early animals long before humans evolved.
As they replicate, they insert themselves at different places in the genome. Depending on where they jump to, they can disrupt normal genes and cause disease - hence the need to keep them in check.
Scientists believe jumping genes account for at least half the human genetic code.
"There have been successive waves of retrotransposon activity in primate evolution, when a transposable element changed to become expressed and replicated itself throughout the genome until something turned it off," she added.
"We've discovered a major mechanism by which the genome is able to shut down these mobile DNA elements."
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