Final answer:
Homozygous genotypes have two identical alleles, either dominant or recessive, for a specific trait, while heterozygous genotypes have two different alleles. For example, TT represents homozygous dominant, tt represents homozygous recessive, and Tt represents heterozygous.
Step-by-step explanation:
In genetics, homozygous and heterozygous genotypes refer to the combination of alleles for a specific gene. When an organism has two identical alleles for a trait, it is homozygous (either homozygous dominant or homozygous recessive). For example, if the genotype for a certain trait is TT, the organism is homozygous dominant, and if it is tt, the organism is homozygous recessive. On the other hand, when an organism has two different alleles for a trait, it is heterozygous.