In 1990, after 17 years of painstaking work, geneticist Mary-Claire King (born 1946) announced that she was close to pinpointing the location of a gene that is responsible for some cases of inherited breast and ovarian cancer. Her work cleared the path for future research aimed at predicting who might be at higher risk for developing the disease and possibly devising better treatments.

Mary-Claire King was born on February 27, 1946, in Evanston, Illinois, a suburb of Chicago, to Harvey W. and Clarice King. The family included a brother, Paul, who later became a mathematician and business consultant, as well as a stepbrother and stepsister. King's father worked at Standard Oil of Indiana managing the personnel department. King studied mathematics at Carleton College in Northfield, Minnesota, graduating Phi Beta Kappa in 1966. Eager for a challenge, she enrolled in graduate school, studying biostatistics at the University of California at Berkeley, where she planned to...