How can an individual with an autosomal dominant trait be identified?

An individual with an autosomal dominant trait can be identified by the presence of at least one affected allele. In genetics, autosomal dominant traits require only one copy of the dominant allele for the phenotype to be expressed. This means that if an individual inherits a dominant allele from either parent, they will display the trait associated with that allele.

For example, if a trait is caused by a dominant allele "A", an individual who has either the genotype "AA" (homozygous dominant) or "Aa" (heterozygous) will both show the trait. In contrast, only individuals with the genotype "aa" (homozygous recessive) would not exhibit the dominant phenotype if the other options proposed specific conditions that do not apply to the expression of dominant traits.

By focusing on the individual with at least one affected allele, it highlights the fundamental principle of inheritance associated with autosomal dominant traits.