Nonetheless, the search for the breast cancer susceptibility gene was moving forward with firm steps in King's lab and accelerating in the mid-1980s. On the basis of a series of unselected breast cancer cases and their family history, in 1988, King's team published a genetic epidemiological model for breast cancer, demonstrating the theoretical existence of a major dominant gene that conferred a high degree of susceptibility to breast cancer in a subset of the population. Applying this genetic penetrance model and using the genotyping technology available at the time, King's team evaluated more than 170 genetic markers, utilizing the gene mapping technique known as linkage analysis. When they in 1990 finally found a genetic marker that showed strong evidence in a subset of families, King's group demonstrated that a single gene on chromosome 17 could be linked to many breast and ovarian cancers, and that genetic heterogeneity was present in breast cancer etiology. A team member suggested that they reorganize their data by age of onset, as in the study cohort, the families in which members had developed cancer at a relatively young age tended to show stronger evidence of linkage to this locus. The idea was that early cases might be more likely to reflect a genetic component, in contrast to sporadic mutations that might occur at any age or even accrue over time. As many as 5-10% of all cases of breast cancer may be hereditary. In 1991 King officially named the gene BRCA1.