**Core Concept**
Autosomal dominant disorders are characterized by the presence of a single copy of the mutated gene, which is sufficient to cause the condition. This type of inheritance follows a dominant pattern, where the affected individual has a 50% chance of passing the mutated gene to each offspring.

**Why the Correct Answer is Right**
Autosomal dominant disorders often result from mutations in genes that encode proteins essential for various cellular processes. The mutated gene can lead to an abnormal protein product that disrupts normal cellular function, causing the disease phenotype. Examples of autosomal dominant disorders include Marfan syndrome, neurofibromatosis type 1, and Huntington's disease.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Marfan syndrome is indeed an autosomal dominant disorder caused by mutations in the FBN1 gene.
**Option B:** This option is incorrect because Neurofibromatosis type 1 is also an autosomal dominant disorder caused by mutations in the NF1 gene.
**Option C:** This option is incorrect because Huntington's disease is an autosomal dominant disorder caused by an expansion of CAG repeats in the HTT gene.

**Clinical Pearl / High-Yield Fact**
It is essential to remember that autosomal dominant disorders often have a high penetrance, meaning that the presence of the mutated gene typically results in the manifestation of the disease phenotype.

**Correct Answer:** D