A novel gene containing a trinucleotide repeat that is expanded and unstable on Huntington's disease chromosomes.

Identification by the many scientists in The Huntington's Disease Collaborative Research Group, including Gusella, of the single defective gene on chromosome 4 that causes the progressive brain disorder, Huntington's disease. The defect is dominant, meaning that anyone who inherits it from a parent with Huntington's will eventually develop the disease. The defective gene codes for a protein called huntingtin. Since identification of the defective gene, a diagnostic genetic test has been developed that can detect the defective gene in people who do not yet have symptoms of the disease.