Educator Henry Louis Gates Jr. has hosted a number of series for PBS that examine American culture and history. In ``Finding Your Roots,'' the Harvard professor continues his quest to ``get into the DNA of American culture,'' as he describes it. In each episode, a celebrity pair -- bound together by an intimate, and sometimes hidden, link -- wades through layers of ancestral history to uncover secrets and surprises from their family trees, sharing life-altering discoveries with viewers. The celebrities discover unknown family histories and relatives they never knew existed. By analyzing each participant's genetic code, DNA diagnosticians trace bloodlines and occasionally debunk long-held beliefs. Among the celebrities featured in the 10-part series are Kevin Bacon, Robert Downey Jr., Martha Stewart and Barbara Walters.