Key Takeaways:

Mary F. Lyon was a pioneering female scientist in the 20th century who is now known for the discovery of X-chromosome inactivation.
Lyon entered academia at a turning point in the male-dominated field.
Despite fulfilling all of the same rigorous academic requirements as her male peers, Lyon received only a "titular degree" in place of a bachelor's degree.
Lyon persevered through personal and professional hardships and was able to establish a name for herself in the field of biology, becoming a pioneering female geneticist of the 20th century.
Lyon’s profound contributions to science are remembered today through the UK Genetics Society’s Mary Lyon Medal.

Mary Frances Lyon was born on May 15th, 1925. In 1943, Lyon enrolled at Girton College—a woman’s only constituent campus of Cambridge University, studying a variety of scientistic disciplines. Lyon primarily focused on zoology, taking particular interest in the role of genetics on the embryology/morphology of animals.

Whilst enrolled at Girton, Lyon experienced the effects of institutional misogyny—being underrepresented and underrecognized throughout. Mary Lyon strove against the cultural sexism 20th century academia presented—being granted only a “titular degree,” for her efforts. In mid-20th-century England, women were commonly thought to lack the stamina, stability, and intelligence deemed necessary for conducting reliable science/experiments.

Figure 1: Water Colour of Girton College

Figure 2: X-Inactivation process

Following completion of her undergrad at Girton, Lyon began her graduate studies in genetics at the University of Cambridge. Mary Lyon’s most notable research involved her study of X-chromosome inactivation in mammals. This theory directly explained the mosaic colouring present in some female—but not male—animals. However, the scope of this discovery goes far beyond this one example, with her original article in Nature being cited in nearly 3000 other articles.

Mosaic colour patterns can be explained by Lyon’s findings on X-chromosome inactivation: as X-chromosome inactivation is random, females—possessing two X-chromosomes—will variably express one of two different genotypes.

Picture References

Header: Created by our Queen Ari on Canva.

Figure 1. Taherian M, Maghsoudi H, Bidaki K, Taherian R. 2016. The Relationship between Skewed X-chromosome Inactivation and Neurological Disorders Development: A Review. International Clinical Neuroscience Journal. 3(2):81–91. doi:https://doi.org/10.22037/icnj.v3i2.13542. [accessed 2022 Jan 13]. https://journals.sbmu.ac.ir/Neuroscience/article/view/13542.

Figure 2. Waterhouse A. Water colour of Girton College, Cambridge. Jewish Women’s Archive. [accessed 2023 Dec 5]. https://jwa.org/media/water-color-girton-college-cambridge.

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