What is a dominant trait represented by?

A dominant trait is represented by a capital letter in genetic notation. This convention indicates that the dominant allele is present, which will express its phenotype even if only one copy is present (heterozygous condition). In contrast, a recessive trait, requiring two copies of the same allele to be expressed, is represented by a lowercase letter. The use of capital and lowercase letters is a fundamental aspect of Mendelian genetics, helping to distinguish between dominant and recessive traits clearly.

The option referring to only two alleles is not accurate for defining dominance, as a trait can have multiple alleles, but the principle of dominance applies specifically to how alleles interact. The description of the phenotype does not represent the trait genetically but rather its observable characteristics, so it does not clarify whether a trait is dominant or recessive in genetic terms.