**Core Concept**
Huntington's chorea, also known as Huntington's disease, is a neurodegenerative disorder characterized by progressive damage to the brain, leading to motor dysfunction, cognitive decline, and psychiatric symptoms. At the molecular level, it is caused by an expansion of a CAG repeat in the Huntingtin gene, resulting in a toxic protein that leads to neuronal death.

**Why the Correct Answer is Right**
Huntington's disease is an autosomal dominant disorder, meaning that a single copy of the mutated gene is sufficient to cause the disease. This is because the mutated gene is expressed from both alleles in a heterozygous individual, resulting in excessive production of the toxic protein. The CAG repeat expansion leads to a polyglutamine stretch in the Huntingtin protein, which is toxic to neurons and causes the characteristic symptoms of the disease.

**Why Each Wrong Option is Incorrect**
**Option A:** Duchenne muscular dystrophy is an X-linked recessive disorder, caused by a mutation in the dystrophin gene. It primarily affects males, as they have only one X chromosome.
**Option B:** Fragile X syndrome is an X-linked disorder, caused by a mutation in the FMR1 gene. It is the most common cause of inherited intellectual disability and is characterized by physical and behavioral abnormalities.
**Option C:** Fanconi's syndrome is a disorder of the proximal renal tubules, characterized by impaired reabsorption of glucose, amino acids, and phosphate. It is usually acquired, but can be inherited in an autosomal recessive pattern.

**Clinical Pearl / High-Yield Fact**
Huntington's disease has a characteristic "cogwheel" rigidity and chorea, which is a type of involuntary movement. The disease is also associated with psychiatric symptoms, such as depression, anxiety, and personality changes.

**✓ Correct Answer: D. Huntington's chorea**