Final answer:
The gene responsible for Huntington's disease is located on chromosome 4, and the condition is passed on in an autosomal dominant pattern, meaning one mutated gene is enough to cause the disease.
Step-by-step explanation:
The Gene Responsible for Huntington's Disease:
The gene responsible for Huntington's disease is found on chromosome 4. This is a classic case of an autosomal dominant genetic disorder, which means that the presence of a single abnormal copy of the Huntington gene (allele) is sufficient to cause the disorder. Individuals with one defective gene (heterozygous for the Huntington allele) will inevitably develop Huntington's disease, typically manifesting symptoms in midlife.
Given this dominant inheritance pattern, offspring have a 50 percent chance of inheriting the condition if one parent carries the Huntington allele. The Huntington gene mutation is characterized by the production of an abnormal protein with an expanded sequence of glutamine residues, a condition that has a cytotoxic effect on neurons, leading to a progressive breakdown of the nervous system.