This shows Brown University researchers studying the biology of aging have found that over time, mouse cells loosened control over parasitic "retrotransposable elements " in the genome. The genomes of organisms from humans to corn are replete with "parasitic" strands of DNA that, when not suppressed, copy themselves and spread throughout the genome, potentially affecting health. Earlier this year Brown University researchers found that these "retrotransposable elements" were increasingly able to break free of the genome's control in cultures of human cells. Now in a new paper in the journal Aging, they show that RTEs are increasingly able to break free and copy themselves in the tissues of mice as the animals aged. In further experiments the biologists showed that this activity was readily apparent in cancerous tumors, but that it also could be reduced by restricting calories.