Autosomal dominant disorder

Definition

An autosomal dominant disorder is a type of genetic condition that is caused by a mutation in one copy of a gene located on one of the non-sex chromosomes, or autosomes. For an individual to be affected by this disorder, only one copy of the mutated gene inherited from an affected parent is sufficient. This leads to the condition being passed down through generations, often with a 50% chance of inheritance for each offspring.

5 Must Know Facts For Your Next Test

1. Autosomal dominant disorders typically manifest in every generation, as affected individuals have a 50% chance to pass the mutation to their children.
2. Common examples of autosomal dominant disorders include Huntington's disease, Marfan syndrome, and familial hypercholesterolemia.
3. An individual with an autosomal dominant disorder can have either one affected parent or may have a new mutation that occurred in their own gametes.
4. Not all individuals who inherit the mutated gene will show symptoms due to variability in penetrance and expressivity of the disorder.
5. Genetic testing can confirm the presence of mutations responsible for autosomal dominant disorders, allowing for early diagnosis and management.

Review Questions

• How does the inheritance pattern of autosomal dominant disorders differ from that of autosomal recessive disorders?
  • In autosomal dominant disorders, only one mutated copy of the gene from an affected parent is necessary for an individual to express the disorder, resulting in a 50% chance of passing it to offspring. In contrast, autosomal recessive disorders require both copies of the gene to be mutated for the phenotype to appear, meaning that two carrier parents have a 25% chance of having an affected child. This difference leads to distinct family inheritance patterns and clinical presentations for each type.
• Discuss the implications of variable expressivity and incomplete penetrance in the context of autosomal dominant disorders.
  • Variable expressivity refers to the range of symptoms that can occur in individuals with the same genetic mutation. In autosomal dominant disorders, this means that two people with the same mutation might experience different severity or types of symptoms. Incomplete penetrance means that not all individuals with the mutation will exhibit symptoms at all. Together, these factors complicate genetic counseling and risk assessment for families since they can lead to unpredictability in how a disorder affects different family members.
• Evaluate the significance of genetic testing for individuals at risk for autosomal dominant disorders and its impact on family planning.
  • Genetic testing for autosomal dominant disorders plays a crucial role in identifying individuals who carry mutations even before symptoms appear. This information allows for informed family planning decisions, as potential parents can understand their risks of passing on conditions such as Huntington's disease. Furthermore, early diagnosis through testing can lead to proactive management strategies and therapeutic interventions, ultimately improving quality of life and outcomes for affected individuals.

Related terms

Autosome: Any chromosome that is not a sex chromosome; humans have 22 pairs of autosomes.

Homozygous:

A genetic condition where an individual has two identical alleles for a particular gene, one from each parent.

Penetrance: The proportion of individuals with a specific genotype who exhibit the associated phenotype; it can vary widely among autosomal dominant disorders.