Which statement best describes autosomal dominant inheritance?

• A. An affected person has a mutation in one copy of the gene.
• B. The trait is never transmitted from parent to child.
• C. It requires two mutated copies for disease expression.
• D. It affects only males.

Answer: (A)

Autosomal dominant inheritance is when one mutated allele is enough to produce the trait. An affected person usually has one mutated copy and one normal copy, and can pass the condition to about half of their offspring, with no bias for sex since the gene is on an autosome. The statement that best fits this pattern is that an affected person has a mutation in one copy of the gene. The other options describe different inheritance patterns: it is not never transmitted, it does not require two mutated copies, and it does not affect only males.