What has 2 genes or alleles like TT or tt?

An organism with two genes or alleles, such as TT or tt, is said to be homozygous for a particular trait. In this case, TT represents a homozygous dominant genotype, while tt represents a homozygous recessive genotype. These genotypes can influence the organism's phenotype, or observable characteristics, depending on the dominance of the alleles involved. For example, if T is dominant over t, the phenotype of TT and Tt would be the same, while tt would have a different phenotype.