What is one key feature of a dominant allele?

A dominant allele is characterized by its ability to influence the phenotype of an organism even when present in just one copy. This property allows dominant alleles to 'mask' the effect of a recessive allele when both are present in a heterozygous genotype. In other words, if an individual has one dominant allele and one recessive allele for a specific trait, the dominant trait will be expressed, while the recessive trait will not manifest in the phenotype.

This masking effect is crucial in understanding inheritance patterns, as it indicates that the presence of a single dominant allele is sufficient to exhibit the trait associated with that allele. This key feature plays a vital role in classical genetics and helps explain why some traits appear more frequently in populations, but it does not imply that a dominant allele is always more frequent.

Other options may suggest limitations on the expression or frequency of dominant alleles, but the ability to mask recessive alleles fundamentally defines their dominant nature.