**Question:** Following is transmitted as autosomal dominant disorder

A. Cystic Fibrosis
B. Marfan's Syndrome
C. Huntington's Disease
D. Wilson's Disease

**Core Concept:** Autosomal Dominant Disorders

Autosomal dominant disorders are genetic conditions where an affected gene is located on one of the non-sex chromosomes (autosomes). These disorders are inherited in a specific pattern, where an affected parent has a 50% chance of passing the condition to each of their children.

**Why the Correct Answer is Right:**

C. Huntington's Disease is transmitted as an autosomal dominant disorder. In this case, the genetic defect is caused by a single nucleotide substitution (CAG trinucleotide repeat expansion) on chromosome 4p16.3. The expansion of the CAG repeat length leads to the production of an abnormally shaped huntingtin protein, which causes neuronal dysfunction and death in specific brain regions, leading to the clinical features of Huntington's Disease.

**Why Each Wrong Option is Incorrect:**

A. Cystic Fibrosis is inherited in an autosomal recessive pattern. In this case, both parents must carry the mutated gene to have a child with the condition, resulting in a 25% chance of offspring being affected, 50% being carriers, and 25% not having the gene.

B. Marfan's Syndrome is inherited in an autosomal dominant pattern, but it is caused by mutations in the FBN1 gene, which is located on chromosome 15q21.1.

D. Wilson's Disease is inherited in an autosomal recessive pattern, meaning that both parents must carry the mutated gene for a child to be affected.

**Clinical Pearl:**

Understanding the inheritance patterns of genetic disorders is crucial to predict the risk of the condition in offspring and to make informed decisions regarding genetic counseling. Autosomal dominant disorders require only one affected parent, while autosomal recessive disorders demand two affected parents. X-linked dominant and X-linked recessive disorders are inherited through the X chromosome.

**Correct Answer:** C. Huntington's Disease is transmitted as an autosomal dominant disorder, which means that an affected individual has a 50% chance of passing the condition to their offspring.