Dr Mary-Claire King: Genetic Pioneer Who Linked BRCA1 to Hereditary Breast Cancer

Dr Mary-Claire King (born 27 February 1946) is an American geneticist whose research established the first definitive link between inherited genetic mutations and breast cancer. Her discovery of the chromosomal location of BRCA1 transformed cancer genetics, proving that susceptibility to breast and ovarian cancer can be inherited and fundamentally changing risk prediction, screening, and preventive care worldwide.

Early Life and Education

Mary-Claire King was born in Illinois, United States, in 1946. She demonstrated an early aptitude for mathematics and analytical reasoning, initially pursuing mathematics as her primary academic interest. She earned her Bachelor of Arts in Mathematics from Carleton College before enrolling at the University of California, Berkeley, where she shifted her focus to genetics (Encyclopaedia Britannica, 2024).

King completed her PhD in genetics in 1973 under the supervision of evolutionary biologist Allan Wilson. During her doctoral research, she made a landmark contribution to evolutionary genetics by demonstrating that humans and chimpanzees share approximately 99% of their DNA, highlighting the close genetic relationship between the two species (King & Wilson, 1975).

Discovering the Genetic Basis of Breast Cancer

In the 1970s, breast cancer was widely regarded as a complex disease influenced primarily by environmental and hormonal factors. The idea that a single gene could strongly predispose individuals to cancer was controversial. King undertook a decades-long investigation into families with unusually high rates of breast and ovarian cancer, using statistical genetics and linkage analysis to test the hypothesis that heredity played a central role (National Cancer Institute, 2023).

In 1990, King and her colleagues identified a region on chromosome 17 that was strongly associated with inherited breast and ovarian cancer — the locus that would later be named BRCA1. Although the gene itself was cloned several years later by other research teams, King’s work proved conclusively that breast cancer can be inherited and that specific genetic mutations dramatically increase cancer risk (Hall et al., 1990).

This discovery marked a turning point in oncology. It enabled the development of genetic testing for cancer susceptibility, allowing individuals with BRCA1 mutations to benefit from earlier surveillance, preventive surgery, and personalised treatment strategies.

Career and Broader Contributions

King held faculty positions at the University of California, Berkeley, before joining the University of Washington School of Medicine in 1995, where she became the American Cancer Society Professor of Genome Sciences and Medicine (University of Washington, 2022).

Her scientific contributions extend well beyond cancer genetics. King has conducted influential research into the genetic basis of schizophrenia, inherited deafness, and HIV resistance, and has pioneered the use of DNA analysis in human rights investigations. Most notably, she developed genetic techniques to identify children who were abducted during Argentina’s military dictatorship, enabling families to be reunited decades later (American Academy of Arts & Sciences, 2021).

Recognition and Legacy

Dr King’s work has been recognised with numerous international honours, including election to the US National Academy of Sciences and the Albert Lasker Award for Clinical Medical Research, awarded for her discovery of the BRCA1 gene and its role in hereditary cancer (Lasker Foundation, 2014).

Today, BRCA1 testing is an integral part of cancer care across the world, influencing decisions about screening, prevention, and treatment for millions of people. King’s research not only reshaped medical genetics but also demonstrated how scientific discovery can be applied ethically in medicine, public health, and human rights.

Her career stands as a defining example of how persistence, rigorous analysis, and interdisciplinary thinking can fundamentally alter our understanding of disease — and save lives.

References

• American Academy of Arts & Sciences. (2021). Mary-Claire King. https://www.amacad.org

• Encyclopaedia Britannica. (2024). Mary-Claire King. https://www.britannica.com

• Hall, J. M., Lee, M. K., Newman, B., et al. (1990). Linkage of early-onset familial breast cancer to chromosome 17q21. Science, 250(4988), 1684–1689.

• King, M.-C., & Wilson, A. C. (1975). Evolution at two levels in humans and chimpanzees. Science, 188(4184), 107–116.

• Lasker Foundation. (2014). Mary-Claire King – Lasker Award Laureate. https://laskerfoundation.org

• National Cancer Institute. (2023). Mary-Claire King, PhD. https://prevention.cancer.gov

• University of Washington. (2022). Mary-Claire King biography. https://www.gs.washington.edu