Zygosity refers to the similarity or dissimilarity of the DNA sequences in specific coding segments, or genes, on the homologous chromosomes of a zygote, or fertilized egg. The DNA sequence of any gene can vary among individuals in the population. The various forms of a gene are called alleles, and diploid organisms generally have two alleles for each gene, one on each of the two homologous chromosomes on which the gene's present. In diploid organisms, the alleles are inherited from the individ… (More on Heterozygous)