The Nancy Guthrie investigation could hang on a strand of DNA

One hundred days is an agonizingly long time for a family to go without answers about their missing loved one. It's also long enough for the investigators working the case to feel the grind. At the 100-day mark, the investigation into the disappearance of Nancy Guthrie could hang on a strand of DNA that's still being evaluated by scientists at the FBI laboratory in Quantico, Virginia, in hopes of identifying her abductor. …