Complex sentence: Doggett finds a strange disfigured man in the X-Files office; believing he is Mulder, Scully has his DNA tested, and the results reveal him to have the same pattern as Mulder.
Split into simpler sentences: Doggett finds a strange disfigured man in the X-Files office; believing he is Mulder, they test his DNA. The test reveals him to have the same pattern as Mulder.