Autosomal recessive

Definition

Autosomal recessive refers to a pattern of inheritance where two copies of a mutated gene (one from each parent) must be present for an individual to express the trait or disorder. This type of inheritance is critical in understanding single-gene disorders, where specific genetic mutations lead to health issues, and it can also play a role in multifactorial conditions, where multiple genetic and environmental factors contribute to the disease's manifestation.

5 Must Know Facts For Your Next Test

1. In autosomal recessive inheritance, both parents must either be carriers or affected by the disorder for their child to be at risk of expressing the trait.
2. Common examples of autosomal recessive disorders include cystic fibrosis, sickle cell anemia, and Tay-Sachs disease.
3. Individuals with one mutated gene (carriers) do not typically show symptoms, making it challenging to identify at-risk individuals in the population.
4. The likelihood of offspring being affected by an autosomal recessive disorder is 25% if both parents are carriers.
5. Genetic counseling is often recommended for families with a history of autosomal recessive disorders to understand the risks and implications.

Review Questions

• How does autosomal recessive inheritance differ from autosomal dominant inheritance in terms of gene expression and carrier status?
  • Autosomal recessive inheritance requires that an individual has two copies of the mutated gene to express the disorder, whereas autosomal dominant inheritance only needs one copy for the trait to manifest. In autosomal recessive cases, carriers with only one mutated allele do not show symptoms, while in autosomal dominant cases, having just one mutated allele can lead to the observable condition. This difference significantly affects how these disorders are inherited and identified in families.
• Discuss the implications of being a carrier for an autosomal recessive disorder in terms of family planning and genetic counseling.
  • Being a carrier for an autosomal recessive disorder means that an individual has one normal and one mutated allele but typically does not exhibit symptoms. For family planning, this status is crucial because if both partners are carriers, they have a 25% chance of having an affected child. Genetic counseling helps families understand their risks, explore testing options, and make informed decisions regarding reproduction and health management for potential offspring.
• Evaluate how environmental factors might interact with genetic predisposition in conditions associated with autosomal recessive inheritance.
  • Conditions linked to autosomal recessive inheritance can sometimes be influenced by environmental factors alongside genetic predisposition. For instance, while cystic fibrosis is primarily driven by genetic mutations, environmental triggers such as infections and pollutants can exacerbate symptoms and health outcomes. Understanding these interactions highlights the complexity of disease manifestation and emphasizes the need for a holistic approach in treatment that considers both genetic makeup and environmental influences.

Related terms

Homozygous: An individual is homozygous when they have two identical alleles for a particular gene, which can lead to the expression of autosomal recessive disorders if both alleles are mutated.

Carrier: A carrier is an individual who has one copy of a mutated gene for a recessive disorder but does not exhibit symptoms because the other allele is normal.

Phenotype: The phenotype is the observable physical or biochemical characteristics of an individual, which can be influenced by autosomal recessive genes.