How do dominant alleles differ from recessive alleles?

Dominant alleles are those that express their traits in a heterozygous individual, meaning that only one copy of the dominant allele is necessary for the trait to be observed in the phenotype. In contrast, recessive alleles require two copies (homozygous condition) to manifest in the phenotype. This means that an individual must inherit the recessive allele from both parents for the characteristic associated with that allele to be expressed.

Understanding this distinction is crucial in genetics, as it helps explain patterns of inheritance and the likelihood of certain traits appearing in offspring based on their genetic makeup. This fundamental principle underlies Mendelian genetics, which frames much of our understanding of heredity.