Homozygous and heterozygous are terms that are used to describe allele pairs. Individuals carrying two identical alleles (RR or rr) are known as homozygous. While individual organisms bearing different alleles (Rr) are known as heterozygous.For example, assume gene of hair colour has two alleles, one of the allele codes for brown (R) and the other codes for black (r).Homozygous will have the same colour alleles on homologous pairs, i.e. ‘RR’ or ‘rr’ and the heterozygous will have different alleles on homologous pair of chromosomes, i.e., Rr.In this article, let us discuss the difference between homozygous and heterozygous.