In a Heterozygous Allele, both Alleles are different in their Genotype. One of them may be dominant while the other carries a recessive trait. Thus, following Mendelian laws of genetics, they will express the dominant features of the dominant Allele present in the Heterozygous pair. In the case of Homozygous pairs of Alleles, the two Alleles carry the same Genotype such that either both of them are dominant Genotypes or both are recessive Genotypes. In such cases, the expression is either a recessive phenotype or a dominant phenotype. One important thing to note is that they are “pure” for a genetic trait and will pass the same (either full dominant or full recessive) Allele to all its progeny.