Huntington's Disease: Chromosome 4 & CAG Repeat Mutation

The Huntington's Disease mutation is a CAG trinucleotide repeat expansion on the short arm of chromosome 4, specifically in the huntingtin (HTT) gene. The normal HTT gene contains up to 35 CAG repeats, while individuals with Huntington's Disease have an expanded repeat with more than 39 CAG repeats.

As the name suggests, Huntington's Disease is the disease associated with this mutation. It's an autosomal dominant neurodegenerative disorder characterized by involuntary movements, impaired cognition, and psychiatric disturbances. The expanded CAG repeat results in the production of a mutant huntingtin protein with abnormal function and accumulation within neurons, leading to neurotoxicity and cell death.