When parents provide a different allele of a given gene, then the offspring is called as heterozygous for that allele. Alleles turn out phenotypes or physical versions of an attribute that are either dominant or recessive.
The dominance or recessivity related to a specific allele is the result of masking, by that, a dominant phenotype hides a recessive phenotype. By this logic, in heterozygous offspring, solely the dominant phenotype is apparent.
