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Mary Lyon chosen as a ‘Heroine of Science’

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Mary Lyon chosen as a ‘Heroine of Science’ Sixth form students from The Abbey School in Reading have chosen to enter Mary Lyon as their ‘Heroine of Science’ for a National Science and Engineering Week competition at the University of Reading. On Tuesday 18 February, they visited Harwell to find out more about her life here and the incredible discovery she made. Mary Lyon was a truly inspirational scientist. At a time when very few women worked in science, she graduated from Cambridge University in 1946 and went on to study for a PhD in genetics. She specialised in genetics, a route which led her to MRC Harwell, then a centre for research into the genetic effects of radiation. During her time at Harwell, she developed her theory of X-chromosome inactivation, also known as Lyonization, and in 1961 published it in Nature. Her discovery led to great advances in our understanding of X-linked inherited diseases such as haemophilia, Duchenne muscular dystrophy, fragile X syndrome and certain cancers. In recognition of her achievement, the Mary Lyon Centre at Harwell is named after her, she is a Fellow of the Royal Society and in 1984 she received their Royal Medal, and she has been awarded the Pearl Meister Greengard Prize, the March of Dimes Prize and the Wolf Prize in Medicine. Despite this, her name is not widely known. Emily Wilson, Stephanie Franklin and Catherine Waldron first became interested in Mary Lyon after reading about her in a book. Driven by a shared interest in genetics, they were inspired by her work and decided to enter her as their Heroine of Science for a competition run by the University of Reading. For this, they must give a short presentation on a female scientist of particular note. When they discovered Mary used to work at Harwell they got in touch to ask if they could visit. “The three of us read the book ‘The Epigenetics Revolution’, and there’s a whole chapter on Mary Lyon and X-inactivation,” said Stephanie. “I think it just caught our imaginations and inspired us to do a bit more research into the woman behind the theories.” One of the clearest examples of X-inactivation Mary used was the genetics of tortoiseshell cats. Like humans, female cats generally have two X-chromosomes (XX), whereas males only have one (XY). Two variants of a gene on the X-chromosome decide whether or not a cat will have a ginger coat. Males either have an entirely ginger or non-ginger coloured coat, as they only have one X-chromosome and one version of the gene, but for tortoiseshell females it is more complicated. One X-chromosome in each cell is randomly inactivated early in development, so the active gene is different in different groups of cells. These then give rise to their characteristic patches of ginger and non-ginger coat. The girls were given a full tour of MRC Harwell, covering both the Mammalian Genetics Unit and the Mary Lyon Centre. In the library they delved into the archives to gain a deeper insight into her life and the events that led up to her discovery. They found the original boards that she used to present her theory of X-inactivation and looked through photographs taken when she was young. One of the girls pulled out a group photo with Mary that we later deduced must have been taken at the Royal Society. The gender imbalance could not have been starker – every other person in the photo was male. To conclude their visit, they had lunch with Peter Glenister, who used to work with Mary at Harwell. They were eager to find out what she was like as a person and he was happy to recall his memories. He described her as an inspirational lady who was always one step ahead. Even though she is now retired, she maintains a strong interest in the science and still reads the current scientific literature. Remembering how she wanted the first computer at Harwell in order to map chromosome bands, Peter said, “Mary Lyon made my career really, and she was full of foresight. We all know what a personal computer is today, but she had the first personal computer here. She had the foresight to see things like that, foresaw the way things would go.” We are proud that the girls have chosen Mary Lyon as their heroine and wish them the best of luck in the competition. We share their hope that this talk will help Mary to receive the recognition she deserves. “We wanted to choose someone that wasn’t well known, someone that deserved more recognition and to be better known,” said Stephanie. “Her work is still having an impact now and there’s so many applications of it. We’re just hoping to make people more aware of that.”

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