Homozygotes are zygotes (a fertilized egg or ovum) that, with regard to a specific gene, contain identical forms (alleles) of that gene at a particular location (locus) on a chromosome. Homozygotes develop into organisms that are homozygous with regard to a particular gene. Homozygotes can also exist as polyploids (organisms with more than two of each type of chromosomes) as long as all of the alleles with respect to a particular gene are identical.

In contrast to homozygotes, heterozygotes contain different alleles of a gene at a particular locus on a chromosome.

Zygotes are diploid cells resulting from the fertilization of a haploid female sex cell (gamete) by a haploid male gamete. In humans, the fusion of an ovum with spermatozoa, each of which contains one chromosome from each parental homologous (corresponding) chromosome pair plus one sex chromosome (i.e., the haploid state), restores the diploid state. Accordingly...