How do dominant alleles express their traits?

Dominant alleles express their traits when at least one copy is present in an individual’s genotype. This means that if an individual carries one dominant allele and one recessive allele for a particular trait, the dominant allele will mask the effect of the recessive one. This fundamental concept is rooted in Mendelian genetics, which illustrates how traits are passed from parents to offspring and how certain alleles can dominate over others.

For instance, if we consider a trait like flower color, where purple (P) is dominant over white (p), both a homozygous dominant (PP) and a heterozygous (Pp) individual will display purple flowers, while only the homozygous recessive (pp) will show white flowers. This clear dominance hierarchy demonstrates why the presence of just one dominant allele is sufficient for the trait to be expressed.