on the X chromosome. This, together with new findings at that time concerning the X chromosome, led her to hypothesize about X chromosome silencing. Lyon published many papers on radiation and chemical mutagenesis and on studies of mutant genes. She also did extensive work on the mouse t-complex. She was head of the Genetics Section of the MRC Radiology Unit at Harwell from 1962 to 1987. Although she retired from research in 1990, according to an interview from 2010, she was still active in the laboratory a few times a week. X-inactivation It was while working on radiation hazards in 1961 that she discovered X-chromosome inactivation, for which she is best known, and the phenomenon is sometimes known as Lyonization in her honour. Her subsequent research helped elucidate the genetic control mechanisms of the X chromosome and helped explain why female 'carriers' of X-linked genetic disorders can display mild symptoms. Awards and honours Lyon was elected a Fellow of the Royal Society in 1973, a Foreign Associate of the US 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. Since 2015 The Genetics Society has awarded the Mary Lyon Medal in her honour. Other awards and honours include: In 1973 Mary Lyon was elected Fellow of the Royal Society. In 1979 she became Foreign Associate of the US National Academy of Sciences. In 1984 she won the Royal Medal of the Royal Society. In 1994 she won the Mauro Baschirotto Award in Human Genetics. In 1997 she was awarded the Wolf Prize in Medicine. In 1997 she also received the Amory Prize. In 2003 Mary was awarded the Mendel Medal by The Genetics Society. In 2004 she was awarded the March of Dimes Prize in Developmental Biology. In 2006 she received the Pearl Meister Greengard Prize. In 2006 she was awarded the Rosenstiel Award, jointly with Davor Solter and Azim Surani. Her nomination for the Royal Society reads: References 1925