DNA testing

When women get a blood test during pregnancy that looks at free-floating DNA, they expect it to tell about the health of the fetus. But the test sometimes finds signs of cancer in the mother. Isabel Seliger for NPR hide caption

Alex, at 4 years and 11 months old, throws a toy football. Caroline Cheung-Yiu hide caption

As mother and daughter, Carmen and Gisele Grayson thought their DNA ancestry tests would be very similar. Boy were they surprised. Meredith Rizzo/NPR hide caption

Czar Nicholas II is shown with his family in the 1910s. All were executed shortly after the 1917 Russian Revolution. Remains of the czar, his wife, Alexandra (top right) and their children — Olga (from left), Maria, Anastasia, Alexei and Tatiana — have all been identified. Now the Russian Orthodox Church has ordered new DNA tests to confirm the identities of Maria and Alexei. Fine Art Images/Heritage Images/Getty Images hide caption

A diver swims in a kelp forest in California's Channel Island National Park, where several of the state's marine protected areas are located. National Park Service hide caption

A Maasai boy and his dog, near the skeleton of an elephant killed by poachers outside of Arusha, Tanzania, in 2013. Jason Straziuso/AP hide caption

Edwin Hopkins with his mother, Alice, and father, Frank Jr. Hopkins was killed aboard the USS Oklahoma during the Japanese bombing of Pearl Harbor, but his remains never were identified. Courtesy Tom Gray hide caption