Which statement describes autosomal dominant inheritance?

• A. Only males are affected.
• B. The disease always skips generations.
• C. A person must have two mutated copies.
• D. A person only needs one copy to be affected.

Answer: (D)

Autosomal dominant inheritance means that inheriting just one copy of a mutated allele on an autosome is enough to express the trait. Because the gene is on an autosome (not a sex chromosome), it affects males and females with equal likelihood, and an affected parent can pass the condition to about half of their children. The pattern typically appears in each generation and does not require two mutated copies.

The statement that a person only needs one copy to be affected captures this idea exactly. In contrast, traits described as only affecting males point to X-linked inheritance, where the gene is on the X chromosome. Traits that skip generations align with autosomal recessive inheritance, where two mutated copies are needed. Traits that require two mutated copies do not describe autosomal dominant inheritance. For example, Huntington disease is a classic autosomal dominant condition.