At the Cincinnati Zoo's Center for Reproduction of Endangered Wildlife, a battle is being waged, and the stakes are higher than life or death. Here, Dr. Betsy Dresser and her colleagues are using cutting-edge reproductive methods in the fight to save species from extinction. TEST TUBE ZOO profiles the challenges they face, and shows the techniques that may mean survival for some of the world's rarest animals. See remarkable footage of an operation that allows a domestic cat to play surrogate mother to a rare baby leopard. In Costa Rica, one family is plagued by a legacy of deafness that researchers hope will lead them to breakthroughs in our understanding of genetics. With a team of geneticists, Dr. Mary Claire King has isolated a single gene responsible for their affliction. In SPIRAL OF SILENCE, join Host Bill Kurtis to explore what this discovery may mean for the future of genetics and humanity.