What principle states that one trait may dominate over another in a pair of alleles?

The principle that states that one trait may dominate over another in a pair of alleles is known as the Law of Dominance. This principle, formulated by Gregor Mendel through his experiments with pea plants, explains that in a pair of alleles, one can mask the expression of the other. The dominant allele will express its trait in the phenotype, while the recessive allele will not show its trait unless in a homozygous state (when both alleles are recessive).

For instance, in Mendel’s pea plant experiments, he observed that when he crossed plants with yellow seeds (dominant trait) and green seeds (recessive trait), all offspring in the first generation had yellow seeds. This occurs because the yellow seed trait masks the green seed trait, illustrating how dominance works in genetics. Understanding this concept is crucial for predicting the outcomes of genetic crosses and understanding inheritance patterns.