## **Core Concept**
Gardner syndrome is a genetic disorder characterized by the presence of multiple colonic polyps (adenomatous polyposis coli), osteomas, skin and soft tissue tumors, and other abnormalities. It is a subtype of familial adenomatous polyposis (FAP). The underlying principle being tested here is the mode of inheritance of this syndrome.

## **Why the Correct Answer is Right**
Gardner syndrome, like FAP, is inherited in an **autosomal dominant** pattern. This means a mutation in one of the two copies of the gene (located on chromosome 5q21-22) is sufficient to cause the condition. The responsible gene is the **APC** (adenomatous polyposis coli) gene, which acts as a tumor suppressor. A single inherited mutated copy of the APC gene leads to the development of hundreds to thousands of polyps in the colon and rectum, significantly increasing the risk of colorectal cancer.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because Gardner syndrome does not follow an autosomal recessive pattern of inheritance. In autosomal recessive disorders, an individual must inherit two mutated copies of the gene (one from each parent) to express the condition.
- **Option B:** This option suggests X-linked dominant inheritance, which is incorrect for Gardner syndrome. X-linked dominant disorders are caused by mutations in genes on the X chromosome, and they typically affect females more frequently than males. Gardner syndrome does not display this pattern.
- **Option C:** This option implies a sporadic pattern, which is not accurate for Gardner syndrome. While some cases may appear sporadic due to de novo mutations, the syndrome itself has a well-defined hereditary component.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that patients with Gardner syndrome are at high risk of developing colorectal cancer, and therefore, prophylactic colectomy is often recommended. Early diagnosis through genetic testing and surveillance can significantly improve outcomes.

## **Correct Answer:** . Autosomal dominant.