Science and personal stories come together to reveal the history of the human genome; patients with rare genetic diseases and their doctors race against time to discover cures.

Geneticists wrestle with moral implications of new technologies that offer both promise and peril; a young scientist with spinal muscular atrophy researches a treatment for her condition.

Part One interweaves the present-day story of the Rosens, a young family on an odyssey to find a cure for their four-year old daughter’s rare genetic disease, with stories of the exciting discoveries of the early pioneers in genetics — Gregor Mendel, Thomas Hunt Morgan, Francis Crick and James Watson.

Part Two continues to interweave stories of patients suffering from rare genetic diseases and the leading researchers racing to identify and treat, even cure, the errors in their DNA that afflict them.

The third part of the four-hour series The Gene: An Intimate History begins with the story of the signature scientific achievement of our time: the mapping of the human genome.

As scientists learn to read the genetic code, they grapple with the dangers inherent in increasingly sophisticated and easily available methods of intervening in the very essence of what makes us human, our DNA.