Autosomal dominant

Definition

Autosomal dominant refers to a pattern of inheritance in genetics where a single copy of a mutated gene located on one of the autosomes (non-sex chromosomes) is sufficient to cause a particular trait or disorder. This means that if one parent carries the mutated gene, there is a 50% chance that each child will inherit the condition, regardless of the sex of the child. This mode of inheritance is crucial in understanding how certain genetic disorders are passed down through generations.

5 Must Know Facts For Your Next Test

1. In autosomal dominant conditions, the trait can be expressed in both males and females equally since the gene is located on an autosome.
2. Examples of autosomal dominant disorders include Huntington's disease, Marfan syndrome, and achondroplasia.
3. An affected individual has a 50% chance of passing the condition to each offspring, meaning every child has an equal chance of inheriting the disorder.
4. New mutations can occur, leading to cases where an affected individual has no family history of the disorder.
5. Some autosomal dominant traits may exhibit variable expressivity, meaning that individuals with the same genotype can have different phenotypes.

Review Questions

• How does autosomal dominant inheritance differ from other modes of inheritance, such as autosomal recessive inheritance?
  • Autosomal dominant inheritance requires only one copy of a mutated gene for the trait to be expressed, while autosomal recessive inheritance requires two copies of the mutated gene (one from each parent) for the trait to manifest. This means that in autosomal dominant conditions, an affected individual has a 50% chance of passing the trait to their offspring regardless of whether they are male or female. In contrast, carriers in autosomal recessive inheritance typically do not show symptoms but can pass on the gene to their children.
• Discuss how penetrance and expressivity impact the observation of autosomal dominant traits in a population.
  • Penetrance refers to the likelihood that individuals with a specific genotype will express the associated phenotype. In cases of autosomal dominant disorders, incomplete penetrance means that some individuals carrying the mutated gene may not show any symptoms at all. Expressivity describes how variable the expression of a trait can be among individuals with the same genotype. Together, these concepts can lead to challenges in predicting disease occurrence within families and understanding how traits manifest in different individuals within a population.
• Evaluate the implications of new mutations in autosomal dominant conditions for genetic counseling practices.
  • The occurrence of new mutations in autosomal dominant conditions presents significant implications for genetic counseling. Genetic counselors must inform families that even if there is no prior family history of a disorder, an individual may still be affected due to a spontaneous mutation. This information is vital for families considering having children, as they need to understand their risks. Additionally, counselors may need to explore and explain issues related to variable expressivity and incomplete penetrance, helping families navigate complex decisions based on their unique genetic backgrounds.

Related terms

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

Penetrance: The proportion of individuals with a specific genotype who exhibit the corresponding phenotype; it describes how often a particular trait appears.

Phenotype: The observable physical and biochemical characteristics of an organism, determined by both genetic makeup and environmental influences.