Here's why:

* Homozygous means having two identical alleles for a particular gene.

* Dominant means that the trait associated with the allele is expressed even if only one copy of the allele is present.

* Recessive means that the trait associated with the allele is only expressed if two copies of the allele are present.

Therefore, homozygous dominant would be represented by two dominant alleles (e.g., AA), while homozygous recessive would be represented by two recessive alleles (e.g., aa).