Answer:
A homozygous dominant trait can be described as a trait in which both the alleles of a gene are the dominant one. For example, the AA genotype of the 80 brown gerbils.
A heterozygous trait can be described as the trait in which one of the alleles is dominant and the other is recessive. For example, the Aa genotype of the 64 brown gerbils.
A recessive trait can be described as a trait in which both the alleles are recessive. For example, the aa genotype of the black gerbils.
The completed table is shown in the attachment.