Betty Jones, 68, is in the terminal stages of Huntington’s disease. She has dementia and is entirely dependent for all aspects of her care. Her daughter, Linda, who is 45 and knows she carries the gene for Huntington’s, has started to develop a loss of coordination. She knows this will get worse, and that soon she will experience the jerkiness which she sees in her mother.

From time to time, Linda, who has been depressed, thinks about suicide. Linda’s son, Martin, now 21, who knows that he has a 50-per-cent chance of inheriting his mother’s dominant genetic disorder, is becoming anxious. He has decided to have the appropriate genetic test.