Credit: USC/Stephanie Kleinman Exposure to mutagens, or mutation-causing agents, can not only bring about changes in DNA but also appear to induce errors when genes are transcribed to make proteins, which may be an important factor in age-related diseases. USC Leonard Davis School of Gerontology Assistant Professor Marc Vermulst and colleagues made the discovery by using state-of-the-art circle sequencing techniques to determine how frequently molecules called RNA polymerases make mistakes when they read (or "transcribe") our DNA. RNA polymerases transcribe DNA to make temporary copies of genes, which are then used to build all of the proteins required to keep us alive and healthy.