In this April 19, 2015 photo, Vicenta Hernandez Gomez sits in a plastic patio chair as she waits to submit a DNA sample to help in the search for her two missing sons, at a local museum that provided the space for a day to conduct the testing, in Iguala, Mexico. One son disappeared on March 1, 2013, and the second on Feb. 6, 2014. According to the government, almost 25,000 people have disappeared in Mexico since 2007 and a lucky few have survived kidnappings. Some have been recovered from mass graves; most remain missing.