**Question:** Wilson's disease is due to mutation in which gene

A. ATP7B
B. HFE
C. ABCD1
D. MUC1

**Correct Answer:** A. ATP7B

**Core Concept:** Wilson's disease is a rare autosomal recessive disorder characterized by copper accumulation in the liver, brain, and other tissues, leading to neurological and psychiatric symptoms. It is caused by mutations in the ATP7B gene, which is responsible for encoding a copper-transporting P-type ATPase protein. This protein is essential for the transport of copper within the cell and across cellular membranes, ensuring proper copper homeostasis.

**Why the Correct Answer is Right:** ATP7B is a crucial gene for maintaining copper homeostasis, as it plays a vital role in copper transport. In Wilson's disease, mutations in ATP7B lead to impaired copper transport, resulting in copper accumulation in tissues and organs. This accumulation triggers the clinical symptoms of the disease.

**Why Each Wrong Option is Incorrect:**

**Option A (HFE):** This option refers to the gene responsible for hemochromatosis, a disorder characterized by iron overload. Hemochromatosis and Wilson's disease are two distinct conditions caused by different genes.

**Option B (ABCD1):** This option is related to X-linked adrenoleukodystrophy (ALD), an inherited disorder caused by mutations in the ABCD1 gene. Wilson's disease is unrelated to this gene.

**Option C (MUC1):** MUC1 is a gene responsible for producing mucin proteins, which are involved in protecting the body's surfaces from damage and pathogens. Wilson's disease is unrelated to this gene.

**Clinical Pearl:** Wilson's disease is a valuable example of how genetic mutations can lead to the development of neurological and psychiatric disorders. Understanding the role of ATP7B in copper homeostasis is crucial for diagnosing and treating Wilson's disease.

**Correct Answer Explanation:** ATP7B is the correct answer because it is the gene responsible for Wilson's disease, a condition causing copper accumulation and clinical symptoms. The other options refer to distinct genetic disorders with unrelated genes, ensuring that understanding the correct answer will help medical students differentiate between different genetic disorders and their respective genes.