With something this rare specialists have seen few cases and we hoped it would become a centre of excellence she says The clinic

"With something this rare, specialists have seen few cases, and we hoped it would become a centre of excellence," she says The clinic did more than that. "Finding the A-T gene was more important than just finding a gene for a rare disease; it would teach us more about the fundamentals of biology," says Sandy Raeburn, Professor of Clinical Genetics at the University of Nottingham, who heads the world's only specialist A-T clinic.That clinic was launched in 1993 by Mrs Watkins and the A-T Society along with the Nottingham team to improve awareness and management of the disease. "It is the flow of information that is so important and it is the human element which provides the spark to push things along," she says.The most difficult question for researchers was how one defective gene could cause so many problems. The trust has raised more than pounds 350,000 and supported work in Professor Yosef Shiloh's laboratory at the Sackler School of Medicine in Tel Aviv, where the gene was finally isolated, and in Dr Taylor's laboratory Mrs Hodson got to know the scientists personally. Some have died from relatively low doses of radiotherapy used to treat the cancer associated with A-T.Mrs Hodson founded the A-T Research Trust in an effort to find out more about the disease. "A-T patients are remarkable for their variety of clinical features," he says.

The unusual list includes abnormalities of the liver, gonads, and endocrine system, susceptibility to cancer and infection as well as showing signs of premature ageing.Another intriguing symptom is that patients are unusually sensitive to damage from X-rays. This is due to degeneration of nerves in the cerebellum, the rear part of the brain responsible for movement and limb control.The disease gets its forbidding name from two symptoms that are characteristic of the disorder: "Ataxia" - the inability to control body movements - and "Telangiectasia", which describes dilation of blood vessels in the whites of the eye and the face.According to Dr Malcolm Taylor from the Institute of Cancer Studies at the University of Birmingham, one of the team that found the gene, there are a host of further complications. As the disease progresses, children have problems eating, writing and speaking as well as walking. By the time he is a teenager he may well be in a wheelchair, like Mrs Watkins's 15-year-old daughter, Sian. His parents first noticed that, as a toddler, he was unsteady on his feet At two, he was diagnosed with A-T and cancer.

Their families are two out of only about 100 in the UK whose children suffer from this progressive degenerative disorder.Mrs Hodson's seven-year-old son, Thomas, is typical. For Beverley Hodson and Glynis Watkins in particular, it is a milestone that stands testimony to years spent fundraising and pushing for progress. It will help unravel the fundamentals of cell biology, generating new insights into common human conditions as diverse as cancer and ageing. It may also cast light on how radiation causes cancer and why some people are more sensitive to radiation than others. For the families of children who suffer from A-T, the discovery is a sign of hope and a reward for past efforts. For researchers, finding the gene for A-T has been likened to the discovery of the Rosetta Stone. Last month, an international team of scientists found the defective gene that causes a rare heritable disorder, Ataxia Telangiectasia (A-T).