How do autosomal dominant disorders differ from autosomal recessive disorders?

Autosomal dominant disorders are characterized by the requirement of only one mutated copy of a gene for the individual to express the disorder. This means that if a person inherits one copy of the mutated gene from either parent, they will display the characteristics of the disorder. In contrast, autosomal recessive disorders necessitate two copies of the mutated gene—one inherited from each parent—for the individual to exhibit the traits associated with the disorder.

This fundamental difference in gene inheritance is crucial for understanding how these disorders manifest and are passed down through generations. For example, a person with an autosomal dominant disorder has a 50% chance of passing the mutation to their offspring, whereas parents with an autosomal recessive disorder must both be carriers of the mutation for their children to be affected, which typically occurs only when both parents contribute a mutated allele.

Understanding this distinction is essential for genetic counseling, as it influences risk assessment and decision-making for families with a history of genetic disorders. The choice that states dominant disorders require one mutated copy highlights this critical genetic principle.