Individuals who have two copies of the same allele are said to be homozygous at that locus. Individuals who receive different alleles from each parent are said to be heterozygous at that locus. The alleles an individual has at a locus is called a genotype.he illustration explores the relationship between the presence of different alleles at a specific locus and an organism's genotype and phenotype. The organism in the model is a plant. It is diploid and the trait is flower color.