Final answer:
Homozygous and heterozygous genotypes refer to the combination of alleles for a particular gene in an organism. Homozygous individuals have two identical alleles, while heterozygous individuals have two different alleles. Phenotypes are the physical characteristics produced by the expression of these alleles.
Step-by-step explanation:
In genetics, homozygous and heterozygous genotypes refer to the combination of alleles for a particular gene in an organism. Homozygous individuals have two identical alleles for a gene, either two dominant alleles (AA) or two recessive alleles (aa). Heterozygous individuals have two different alleles for a gene (Aa).
The expression of these alleles in the genotypes produces phenotypes, which are the physical characteristics of an organism. In the case of Mendelian inheritance, where one allele is dominant and the other is recessive, homozygous dominant and heterozygous individuals will have the same phenotype. The recessive allele will only be observed in homozygous recessive individuals.