Autosomal dominant disorder

Autosomal Dominant Disorder

An autosomal dominant disorder is a type of genetic condition that is passed down through families in an autosomal dominant pattern. This means that only one copy of the altered gene, inherited from either parent, is sufficient to cause the disorder. These disorders are characterized by their inheritance pattern, where the presence of a single mutated allele on one of the autosomes (non-sex chromosomes) can lead to the manifestation of the disease.

Genetics of Autosomal Dominant Disorders

In humans, there are 22 pairs of autosomes and one pair of sex chromosomes. Autosomal dominant disorders are associated with mutations in genes located on the autosomes. Each individual inherits two copies of each gene, one from each parent. In autosomal dominant disorders, a mutation in just one of the two copies of a gene is enough to cause the disorder.

Inheritance Pattern

The inheritance pattern of autosomal dominant disorders is such that an affected individual has a 50% chance of passing the mutated gene to each offspring. This is because the affected individual has one normal allele and one mutated allele, and each child inherits one allele from each parent.

Penetrance and Expressivity

• Penetrance refers to the proportion of individuals with the mutation who exhibit clinical symptoms. Some autosomal dominant disorders have incomplete penetrance, meaning not all individuals with the mutation will show symptoms.
• Expressivity refers to the range of symptoms that can occur in different individuals with the same genetic mutation. Autosomal dominant disorders can have variable expressivity, where symptoms can vary in severity among affected individuals.

Examples of Autosomal Dominant Disorders

Several well-known genetic disorders follow an autosomal dominant inheritance pattern:

• Huntington's disease: A neurodegenerative disorder characterized by motor dysfunction, cognitive decline, and psychiatric symptoms.
• Marfan syndrome: A connective tissue disorder affecting the cardiovascular system, eyes, and skeleton.
• Achondroplasia: A form of short-limbed dwarfism.
• Familial hypercholesterolemia: A disorder characterized by high cholesterol levels, leading to an increased risk of heart disease.

Diagnosis and Management

Diagnosis of autosomal dominant disorders often involves a combination of clinical evaluation, family history, and genetic testing. Genetic counseling is recommended for affected individuals and their families to understand the inheritance pattern and implications for family planning.

Management of these disorders varies depending on the specific condition and may include medical treatment, lifestyle modifications, and supportive therapies. For some conditions, early diagnosis and intervention can significantly improve quality of life.

Also see

• Autosomal recessive disorder
• X-linked dominant disorder
• Genetic counseling
• Genetic testing