Mary Francis Lyon

PC: Jane Gitschier, PLoS Genetics

PC: Jane Gitschier, PLoS Genetics

Ever wonder how calico cats get their unique coloring? This week’s WiSE Wednesday honoree, Mary F. Lyon, did, and she went on to discover the phenomenon, X-chromosome inactivation, that causes it. Thanks to Lyon’s work, we now know that, the beautiful variegated hair we see is the result of random silencing of one copy of the two X chromosomes in each of a female cat’s cells, which causes different pigments to be expressed in different places. Lyon first hypothesized this random X-chromosome inactivation when, as a researcher for the Medical Research Council (MRC) in England, she observed a similar condition in mice. She went on to help elucidate this process’s mechanism, sometimes referred to as “Lyonization,” as well as to make significant contributions in other aspects of genetics, including the effects of radiation on DNA and mechanisms of non-Mendelian inheritance.

Born in England in England in 1925, Lyon was inspired by a schoolteacher to study science. Reading a set of books on nature she won in an essay contest focused her broad curiosity onto the field of biology. She attended Girton College of the University of Cambridge where she studied zoology but, solely because of her gender, was only awarded a “titular” degree. She then started a PhD at Cambridge, finishing her graduate studies at the University of Edinburgh (a move motivated by Edinburgh’s superior histology facilities). While there, she started work with the MRC, then moved to Harwell, where she continued her MRC-funded work until she retired in 1990. Her talent was recognized and she was named head of the MRC Radiology Unit, a position she held for 25 years. Her numerous awards include election as a Fellow of the Royal Society, a Foreign Associate of the National Academy of Sciences, and a Foreign Honorary Member of the American Academy of Arts and Sciences. Although she was forced to retire in 1990 because of her age, she still visited the lab several times per week until shortly before her death.