How does a dominant allele express its trait?

A dominant allele expresses its trait in the presence of at least one dominant allele. This means that if an individual possesses one or two copies of the dominant allele, the corresponding trait will be manifested in the phenotype. This relationship is key in understanding Mendelian genetics, where traits are often described using dominant and recessive alleles.

In contrast, a recessive allele would only express its trait when two copies are present, as it is masked by the presence of a dominant allele. Thus, it is the dominance of certain alleles that allows for specific traits to be consistently expressed when at least one dominant allele is inherited, regardless of the other alleles present. This principle is fundamental in predicting inheritance patterns and understanding genetic variation among individuals.