Huntington's disease is caused by mutation in which gene and what is the inheritance pattern?

• A. HTT gene (autosomal dominant)
• B. APP gene (autosomal recessive)
• C. SNCA gene (autosomal dominant)
• D. MAPT gene (autosomal dominant)

Answer: (A)

Huntington's disease arises from a mutation in the HTT gene, on chromosome 4, specifically an expanded CAG trinucleotide repeat that creates a toxic polyglutamine tract in the huntingtin protein. This genetic change is inherited in an autosomal dominant pattern, so a single mutated allele is enough to cause disease and each child of an affected person has a 50% chance of inheriting it. The condition typically presents in adulthood with chorea, cognitive decline, and psychiatric symptoms, and shows anticipation as repeats expand in subsequent generations, leading to earlier onset over time. The other gene options correspond to different neurodegenerative diseases (APP with Alzheimer's, SNCA with Parkinson-related disorders, MAPT with tauopathies), not Huntington's, making HTT with autosomal dominant inheritance the correct pairing.