**Core Concept**
Mutations in Marfan syndrome are associated with the FBN1 gene, which encodes for fibrillin-1. This protein plays a crucial role in the formation of elastic fibers found in connective tissue. Defects in fibrillin-1 lead to the characteristic features of Marfan syndrome.

**Why the Correct Answer is Right**
The FBN1 gene is a large gene that spans over 70 kilobases and contains 65 exons. Mutations in this gene disrupt the production of fibrillin-1, leading to the accumulation of abnormal elastic fibers in various tissues. This results in the clinical manifestations of Marfan syndrome, including tall stature, long limbs, and a predisposition to aortic aneurysms and dissections.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify the correct gene associated with Marfan syndrome. While other genes may be involved in related disorders, FBN1 is the primary gene mutated in Marfan syndrome.
**Option B:** This option is incorrect because it does not accurately identify the protein encoded by the FBN1 gene. Fibrillin-2 is a related protein, but it is encoded by a different gene (FBN2) and is associated with a distinct disorder called congenital contractual arachnodactyly.
**Option C:** This option is incorrect because it suggests a different gene is associated with Marfan syndrome. While other genes may contribute to the development of related disorders, FBN1 is the primary gene mutated in Marfan syndrome.

**Clinical Pearl / High-Yield Fact**
Fibrillin-1 is a key component of elastic fibers found in connective tissue, and mutations in the FBN1 gene can lead to a range of disorders, including Marfan syndrome, congenital contractual arachnodactyly, and others.

**Correct Answer: C. FBN1 gene**