Why do racial and ethnic controversies become attached, as they often do, to discussions of modern genetics? How do theories about genetic difference become entangled with political debates about cultural and group differences in America? Such issues are a conspicuous part of the histories of three hereditary diseases: Tay-Sachs, commonly identified with Jewish Americans; cystic fibrosis, often labeled a -Caucasian- disease; and sickle cell disease, widely associated with African Americans.

In this captivating account, historians Keith Wailoo and Stephen Pemberton reveal how these...