Johni Cerny, the chief genealogist for the PBS series “Finding Your Roots,” who helped some 200 famous people — among them Oprah Winfrey, Quincy Jones, Senator Bernie Sanders and Speaker Nancy Pelosi — trace their ancestry, died on Wednesday in Lehi, Utah, near Salt Lake City. She was 76.

Deborah Christensen, Ms. Cerny’s partner of 23 years, said the cause was coronary artery disease and congestive heart failure.

“Johni Cerny was the proverbial dean of American genealogical research,” Henry Louis Gates Jr., the Harvard professor who is a host and executive producer of “Finding Your Roots,” said in a statement. In an email message on Thursday, he described her work as “transforming raw data into narratives and metaphors about diversity and our common humanity.”

Ms. Cerny’s passion for the field began in childhood, for intensely personal reasons.

Jonnette Elaine Cerny was born on Aug. 27, 1943, in Kansas City, Mo. Her mother was Vivian Elaine (West) Cerny, and the man she was told was her father was John Steve Cerny, a soldier in World War II who later worked in the heating and air-conditioning business. She was the oldest of five children.