What do dominant alleles accomplish in the context of genetics?

In genetics, dominant alleles play a crucial role in determining phenotypes. When a dominant allele is present in an organism's genotype, it is expressed in the phenotype, meaning the physical and observable characteristics of the organism reflect that dominant trait. This occurs regardless of whether the second allele (from the paired homologous chromosome) is dominant or recessive.

For example, consider a trait controlled by two alleles, one dominant (A) and one recessive (a). If an individual has the genotype AA or Aa, the dominant allele A will dictate the phenotype. Therefore, dominant alleles assert their influence over recessive alleles, which do not manifest in the phenotype when paired with a dominant allele.

Understanding this concept is critical in genetics, as it lays the foundation for predicting inheritance patterns and the likelihood of certain traits appearing in offspring.