**Question:** Which of the following is an autosomal dominant genetic disorder?

A. Cystic Fibrosis
B. Huntington's Disease
C. Pompe Disease
D. Gaucher Disease

**Core Concept:** Autosomal Dominant Genetic Disorders

Autosomal dominant disorders are a type of genetic disorder where the genetic mutation is inherited from one or both parents. In this type of inheritance, an individual only needs to inherit one normal copy of the gene to be healthy, while carriers of the mutated gene will display the symptoms of the disorder.

**Why the Correct Answer is Right:**

**B. Huntington's Disease** is an autosomal dominant genetic disorder caused by a mutation in the HTT gene located on chromosome 4p16.3. The genetic defect results in an abnormal huntingtin protein, which leads to neuronal dysfunction and death in specific brain regions, primarily the striatum and cortex. This results in the characteristic symptoms of Huntington's Disease, including chorea, cognitive decline, and psychiatric symptoms.

**Why Each Wrong Option is Incorrect:**

A. **Cystic Fibrosis** (located on chromosome 7q31.3) is caused by mutations in the CFTR gene and is an autosomal recessive disorder. In autosomal recessive disorders, both copies of the gene must be mutated for the individual to be affected. Autosomal dominant disorders, like Huntington's Disease, only require one mutated gene copy.

C. **Pompe Disease** (located on chromosome 17) is an autosomal recessive disorder caused by mutations in the GAA gene. Autosomal dominant disorders, like Huntington's Disease, require one mutated gene copy, while autosomal recessive disorders need two mutated gene copies.

D. **Gaucher Disease** (located on chromosome 12) is an autosomal recessive disorder caused by mutations in the GBA gene. As mentioned above, autosomal dominant disorders, like Huntington's Disease, need one mutated gene copy, while autosomal recessive disorders need two mutated gene copies.

**Clinical Pearl:**

Autosomal Dominant Disorders are a result of a single gene mutation, while Autosomal Recessive Disorders require two mutations in the same gene. This understanding is crucial in genetic counseling and predicting the risk of offspring with these disorders based on the parents' genotypes.

Understanding the mode of inheritance of genetic disorders is essential for clinical practice as it helps in counseling families and predicting the risk of inheritance in future generations.