By Jahnavi Dalmia, Research Team Member
Mary Frances Lyon, popularly recognized for the phenomenon of ‘Lyonization’ or X chromosome inactivation, was a prominent personality in twentieth-century genetics. Born in Norwich, her career started in 1946, upon her graduation from Cambridge University with a specialization in zoology. Lyon completed her PhD in genetics, and joined Toby Carter, a geneticist, in studying radiation mutagenesis. Later, she transferred to the MRC Radiobiology unit at Hartwell in 1955 and headed the Genetics section there in 1962. It was here that she proposed the concept of X chromosome inactivation, on investigating the patchy fur on female mice. The mottling was explained due to the mosaic distribution of colour genes on one of the pairs of X-chromosomes in each cell.
This phenomenon ensures proper dosage compensation in female mammals by inactivating one X chromosome. This discovery was a cornerstone in the field of genetic regulation owing to its insights into X-linked genetic disorders and the development of organisms. This discovery enabled research on mechanisms, which provide the foundation for modern genomics and molecular medicine. She also contributed significantly to the understanding of the t-complex encoded on chromosome 17 in the mouse genome, which plays a critical part in fertility.
She was awarded the Royal Medal by the Royal Society and the Wolf Prize in Medicine in 1997 for her contributions. In 2004, the Mary Lyon Centre was established in Harwell, recognizing her as one of the leading geneticists of her time. She died on Christmas Day 2014 after suffering from Parkinson’s.
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