Final answer:
Huntington's disease is an inherited neurodegenerative disorder that affects the brain and causes symptoms such as muscle spasms, personality changes, and cognitive decline. The disease typically appears in middle age.
Step-by-step explanation:
Huntington's disease is an inherited neurodegenerative disorder that results in the death of certain neurons in the brain. It is caused by a mutation in the huntingtin gene, which leads to the production of a longer than normal sequence of glutamine residues in the huntingtin protein. The disease is autosomal dominant, meaning that individuals with one copy of the mutated gene will develop the disease.
The symptoms of Huntington's disease typically appear in middle age, around age 40, although they can start earlier or later. These symptoms include muscle spasms, personality changes, and cognitive decline. The disease is progressive and ultimately fatal.