Question

Distinguishing autosomal dominant inheritance from X-linked dominant inheritance in pedigree analysis is often difficult. Which of the following observations would be characteristic of autosomal dominant, but not of X-linked dominant inheritance.

Answer 1

Answer: The difference between autosomal dominant inheritance and X-linked dominant inheritance is in the frequency of occurrence among males and females. Autosomal dominant traits appears in both sexes with equal frequency while in X-linked dominant trait, often more females than males are affected.

Explanation: More females are affected in X-linked dominant trait because affected fathers will pass the trait on to all their daughters, affected daughters must have either an affected mother or an affected father.

In the case of autosomal dominant inheritance, the trait appears in both sexes with roughly equal frequency. Affected offsprings must have an affected parent unless they possess a new mutation.