Funeral for influential British geneticist who proposed X-inactivation

Mary Frances Lyon, mother of X-inactivation, died aged 89 on Christmas Day and her funeral is being held near her home in Oxfordshire today.

Mary Lyon was an early influential British geneticist, completing her studies at Cambridge University at a time when just 500 women were admitted and could only receive “titular” degrees.

She proposed the theory of X-inactivation, also known as Lyonisation, leading to great advances in our understanding of diseases such as haemophilia and Duchenne Muscular Dystrophy.

Her theory of X-inactivation states that one of the two X chromosomes in female mammals is permanently inactivated early in development, so the genes are effectively switched off.

However, which X chromosome is inactivated is random and varies from cell to cell. This is how female cats, but not males, can have tortoiseshell coats.

The theory led to an explanation for why women who are carriers of X-linked diseases can still show symptoms, and was one of the first examples of epigenetics, now a scientific field in its own right.

She was a long-term researcher with the Medical Research Council. She was elected a Fellow of the Royal Society and a Foreign Member of the US National Academy of Sciences.

Her accomplishments have also been widely recognised by many international honours and prizes, including the Royal Medal, the Wolf Prize for Medicine and the Pearl Meister Greengard Prize, an international award to recognise the accomplishments of outstanding women scientists.

Her funeral is being held at 12pm at South Oxfordshire Memorial Park and Crematorium.