Mary F. Lyon

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This article is about the 20th century British geneticist. For the 19th century American educator, see Mary Lyon.
Mary F. Lyon
Mary Frances Lyon.png
Born (1925-05-15) 15 May 1925 (age 89)
Norwich, England
Alma mater Girton College
Doctoral advisor R A Fisher
Known for discovery of X-chromosome inactivation
Notable awards Royal Medal (1984)
William Allan Award (1986)
Wolf Prize in Medicine (1997)

Mary Frances Lyon, FRS (born 15 May 1925) is an English geneticist, who is best known for her discovery of X-chromosome inactivation, an important cytogenetic phenomenon.

Childhood and education[edit]

Mary Lyon was born on 15 May 1925 in Norwich, England as the eldest out of three children of a civil servant and a schoolteacher. She was educated at a grammar school in Birmingham. During that time, she said, she became interested in science thanks to a good schoolteacher[1] and nature books she won in an essay competition.[2] During the second world war, she pursued her studies at Girton College at the University of Cambridge,[3] where she read zoology, physiology, organic chemistry and biochemistry, with zoology as her main subject. Only 500 woman students were allowed to study in the university, in contrast to more than 5000 men. Furthermore, the woman received only a “titular” degree, despite attending the lectures with men, taking the same practical courses and passing the same exams as the men.[2] During that time she became interested in embryology. She went on to do her PhD with R A Fisher, who was Professor of Genetics in Cambridge, where she characterized a mutant mice strain with a 'pallid' mutation and published the reserch. During the course of her PhD she moved to Edinburgh.


After her PhD Mary Lyon joined the group of Conrad Hal Waddington, with whom she workerd in the last part of her PhD. The group was funded by the Medical Research Council to investigate mutagenesis and the genetic risks of radiation. In addition to the 'pallid' mutation mice, she studied mutations such as 'ataxia' (a nervous mutation which caused walking difficulties in the mice) and 'twirler' (a mutation which induced inner ear issues, causing the mice to shake their heads and walk in circles due to lack of balance). In 1955, her group moved to the MRC radiobiology unit in Harwell, where the was room for more mouse facilities. There she continued to investigate the mouse mutations. She also scrutinized a 'mottled' mutant, which had a different effect on male and female mice: male embryos sometime died, and the surviving males had white coats, but females lived and were variegated. Through calculated and deliberated breeding of mutants, she investigated the transition of the mutation and concluded that the mutation was positioned on the X chromosome. This, together with new findings at that time concerning the X chromosome, led her to hypothesize about X chromosome silencing.[2]

Mary lyon has published many papers on radiation and chemical mutagenesis and on studies of mutant genes. She was head of the Genetics Section of the MRC Radiology Unit at Harwell from 1962 to 1987. She retired from active research in 1990. According to an interview from 2010, she still visits the lab a few times a week.[2]

X-inactivation also known as Lyonization[edit]

It was while working on radiation hazards in 1961 that she discovered X-chromosome inactivation, for which she is best known.[3] Her research elucidated the genetic control mechanisms of the X chromosome, which explains the absence of symptoms in numerous healthy women that are carriers of diseases associated with the chromosome. An example of X chromosome deactivation is Duchenne muscular dystrophy. Dr. Lyon has also done extensive work on the mouse t-complex,[4] and made many other contributions to mammalian genetics.


Mary Frances Lyon is a Fellow of the Royal Society, a Foreign Associate of the U.S. National Academy of Sciences, and a Foreign Honorary Member of the American Academy of Arts and Sciences. In 1994 she won the Mauro Baschirotto Award in Human Genetics, in 1997 the Wolf Prize for Medicine, for her hypothesis concerning the random inactivation of X-chromosomes in mammals. In 1997 she also received the Amory Prize, for genetic discoveries relating to mammalian sex chromosomes. In 2004 she was awarded the March of Dimes Prize in Developmental Biology. In 2006 she received the Pearl Meister Greengard Prize awarded by the Rockefeller University.

Awards and recognition[edit]


Gene Action in the X-chromosome of the Mouse (Mus musculus L.) Nature 190, 372 - 373 (22 April 1961).


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  2. ^ a b c d
  3. ^ a b Peter Harper (11 October 2004). "Mary Lyon". Genetics and Medicine Historical Network, Cardiff University. 
  4. ^ Mary F. Lyon (1986). "Male sterility of the mouse t-complex is due to homozygosity of the distorter genes". Cell (Cell Press) 44 (2): 357–363. doi:10.1016/0092-8674(86)90770-1. 


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