**Question:** All of the following are autosomal dominant, except:

A. Coronary artery disease
B. Hypothyroidism
C. Cystic Fibrosis
D. Alzheimer's disease

**Core Concept:** Autosomal Dominant Genetic Disorders

Autosomal dominant disorders are genetic conditions where the affected gene is located on an autosome (non-sex chromosome) and is inherited in a dominant pattern, meaning that an individual with one copy of the mutated gene has a 50% chance of passing the trait to their offspring.

**Why the Correct Answer is Right:**

Autosomal dominant disorders are generally caused by mutations in genes that control the development, function, or maintenance of specific tissues or organs. These mutations can lead to various clinical manifestations depending on the affected organ or system.

**Why Each Wrong Option is Incorrect:**

A. Coronary artery disease (CAD) is generally caused by a combination of genetic, lifestyle, and environmental factors, making it less likely to be classified as an autosomal dominant disorder.
B. Hypothyroidism (underactive thyroid gland) is often related to iodine deficiency, autoimmune disorders, or congenital abnormalities, which are not directly linked to autosomal dominant inheritance.
C. Cystic Fibrosis (CF) is caused by mutations in the CFTR gene (Cystic Fibrosis Transmembrane Conductance Regulator), which is responsible for regulating the movement of chloride ions across cell membranes. Cystic Fibrosis is an autosomal dominant disorder.
D. Alzheimer's disease (AD) is primarily caused by mutations in genes like APP, PSEN1, and PSEN2, which are associated with the amyloid-beta protein and neurofibrillary tangles in the brain, leading to cognitive decline. Alzheimer's disease is mostly sporadic and not typically inherited in an autosomal dominant pattern.

**Clinical Pearl:**

Understanding the inheritance patterns of genetic disorders is essential for proper genetic counseling and disease management. Autosomal dominant disorders are characterized by a 50% chance of inheritance to offspring, while other inheritance patterns like autosomal recessive, X-linked, or mitochondrial disorders exist, each with distinct inheritance patterns and clinical implications. Familiarize yourself with these patterns and their corresponding genes/proteins to accurately diagnose and counsel patients and their families regarding the inheritance of genetic disorders.

**Correct Answer:** D. Alzheimer's disease (neurodegenerative disorder)

In conclusion, Alzheimer's disease is not typically inherited in an autosomal dominant fashion, unlike Cystic Fibrosis (CF), which is an autosomal dominant disorder caused by mutations in the CFTR gene responsible for regulating chloride ion transport across cell membranes. This distinction between autosomal dominant and sporadic cases of Alzheimer's disease is crucial for genetic counseling and patient management.