A plant's ability to survive long days in the sun may rely in part onits ability to repair damage caused by the same ultraviolet raysresponsible for certain skin cancers in humans, according to areport in a recent issue of the journal Science by UC Davis researcher Anne Britt. Scientists have known that certain beneficial solar rays help plants repair the most common kind of ultraviolet DNA damage during the daytime. By isolating for the first time a UV-sensitive mutant strain of a popular research plant, Britt and her colleagues showed that plants need another kind of genetic repair service that can take place in light or darkness. Although this "dark" repair pathway performs well, Britt's technique is expected to shed light on other DNA repair processes that may be faulty. "Paradoxically, DNA repair processes are a source of genetic diversity," says Britt, an assistant research geneticist in plant biology. "The damage itself is not a mutation; a mutation happens when the damage is repaired inaccurately, causing a change in the genetic code."