Human have been infected by so many viruses that 8 present of our DNA is made up of them
Eight percent of our DNA consists of remnants of ancient viruses, and another 40 percent is made up of repetitive strings of genetic letters that is also thought to have a viral origin. An early clue came from the pioneering geneticist Barbara McClintock, who spent much of her career at CSHL. In the 1940s, long before the decoding of the human genome, she realized that some stretches of our DNA behave like infectious invaders. These DNA chunks can move around through the genome, copying and pasting themselves wherever they see fit, which inspired McClintock to call them “jumping genes.” Her once-controversial idea earned her a Nobel Prize in 1983. Geneticists have since determined that jumping genes originate in the viral portion of the genome. Many of these genes turn out to be benign or even helpful. “But some of the things are full-on parasites,” Hammell says, like infections embedded within our own DNA. All it takes to set these bad actors loose, she is finding, is a slip-up i...