Which of the following best describes a dominant phenotype?

A dominant phenotype is best described as traits that are expressed in both homozygous and heterozygous individuals. This means that if an individual carries at least one dominant allele for a particular trait, that trait will be manifested in the individual's phenotype. Dominance refers to the relationship between alleles, where the dominant allele can mask the effects of a recessive allele when they are present together in a heterozygous individual.

For instance, if we consider a trait where "A" represents a dominant allele and "a" represents a recessive allele, individuals with both AA (homozygous dominant) and Aa (heterozygous) will show the dominant trait. Conversely, only individuals with the genotype aa (homozygous recessive) will express the recessive phenotype. This is foundational knowledge in genetics that illustrates how dominance works in terms of phenotypic expression.