Law of Dominance
(genetics) A Mendelian law which holds that one from the pair of alleles coding for a particular trait would be expressed whereas the other is unexpressed. The allele expressed for a particular trait is regarded as the dominant whereas the other (which is unexpressed) is considered recessive.
For instance, a cross between two pure plant breeds for a flower trait of contrasting colors (e.g. blue and white) would result in a progeny (offspring) that bears the two alleles (each inherited from its parents) coding for the blue and white flowers. However, this progeny would produce either blue or white flower. If for instance the dominant color for the flower is blue, then, the allele coding for blue flowers would be expressed whereas the allele for white flowers would not be expressed. In this case, the recessive trait (i.e. white flower) would only be expressed in a progeny when it acquires a pair of recessive alleles from its parents.