Autosomal dominant

Definition

Autosomal dominant refers to a pattern of inheritance in which only one copy of a mutated gene from an affected individual can cause the trait or disorder to manifest in offspring. This mode of inheritance means that each affected individual has a 50% chance of passing the condition to their children, making it crucial in understanding genetic diseases and their transmission within families.

5 Must Know Facts For Your Next Test

1. An individual with an autosomal dominant condition typically has an affected parent, as the mutation is directly inherited.
2. Examples of autosomal dominant disorders include Huntington's disease, Marfan syndrome, and achondroplasia.
3. In the case of autosomal dominant inheritance, males and females are equally likely to be affected and pass on the trait to their offspring.
4. The presence of a single mutated allele is sufficient for phenotypic expression, meaning homozygous individuals may have more severe symptoms than heterozygous individuals.
5. Incomplete penetrance can occur in autosomal dominant traits, meaning not all individuals with the mutation will exhibit symptoms, complicating genetic counseling.

Review Questions

• How does the pattern of inheritance for autosomal dominant traits differ from that of autosomal recessive traits?
  • In autosomal dominant inheritance, only one mutated allele is necessary for the trait to be expressed, meaning an affected individual has a 50% chance of passing it to each child. In contrast, for autosomal recessive traits, two copies of the mutated allele are required for the trait to manifest. As a result, parents who are carriers (heterozygous) may not show any symptoms but can pass on the recessive allele to their offspring.
• What implications does autosomal dominant inheritance have for genetic counseling and family planning?
  • Understanding that an autosomal dominant condition can be inherited with a 50% chance informs genetic counseling significantly. Families with a history of such conditions can seek genetic testing to determine if they carry the mutated gene. This knowledge helps couples make informed decisions regarding family planning, including options such as prenatal testing or considering the use of reproductive technologies to prevent passing on the disorder.
• Evaluate how penetrance impacts the understanding of autosomal dominant disorders in clinical practice.
  • Penetrance plays a critical role in clinical practice regarding autosomal dominant disorders since it determines how consistently a genotype leads to a phenotype. Variations in penetrance can lead to confusion in diagnosis and genetic risk assessment because some individuals may carry the mutation without exhibiting any symptoms. Clinicians must consider this variability when advising patients and families about risks, testing options, and potential outcomes related to genetic conditions.

Related terms

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

Homozygous: Having two identical alleles for a specific gene, which can affect the expression of autosomal dominant traits.

Penetrance: The proportion of individuals carrying a particular genotype that also express the associated phenotype, relevant in assessing the expression of autosomal dominant conditions.