Define a homozygous genotype.

A homozygous genotype refers to an individual having two identical alleles for a particular trait. This means that both alleles can be either dominant or recessive. For example, if an organism has two dominant alleles for a specific trait, such as "AA," or two recessive alleles, such as "aa," it is classified as homozygous. This uniformity at the genetic level often leads to the expression of specific traits consistently, as there is no variation in the alleles that could influence the phenotype differently.

In contrast, the other choices reference different genetic configurations: having two different alleles for a trait is termed heterozygous; possessing one dominant and one recessive allele is a specific type of heterozygous condition; and having multiple alleles refers to situations involving more than two allele forms for a single gene, common in traits governed by multiple alleles. Therefore, the definition of a homozygous genotype aligns perfectly with the correct answer.