What distinguishes dominant alleles from recessive alleles?

Dominant alleles are distinguished from recessive alleles by their ability to express traits even when paired with a different allele, such as a recessive allele. This means that if an individual carries one dominant allele and one recessive allele for a particular trait (heterozygous condition), the dominant trait will still be expressed. This is in contrast to recessive alleles, which only manifest their traits when an individual has two copies of that allele (homozygous condition).

For example, if the dominant allele is for brown eyes and the recessive allele is for blue eyes, a person with one brown-eye allele and one blue-eye allele will have brown eyes, highlighting the dominance of the brown-eye trait. This characteristic of dominant alleles is fundamental in the study of genetics and inheritance, as it determines how traits are expressed in offspring.

In summary, the correct answer emphasizes that dominant alleles have the unique ability to dictate traits regardless of the presence of recessive versions of the gene.