Dr. Carpenter with Scully.
Doctor Anne Carpenter (played by Anne DeSalvo) was a genetic researcher at Georgetown University's Microbiology Department who examined samples from the Purity Control project at the request of Agent Dana Scully. She explained to Scully that the samples she examined had two additional base-pairs and could therefore not have originated from Earth.
She and her family died the next day in a mysterious car accident which was probably a covert assassination (by Crew Cut Man) to prevent the discovery becoming public knowledge.