Final answer:
The expected phenotypic ratios in the offspring of two heterozygous horses for two traits can be determined using a Punnett square. Assuming both alleles are dominant, the expected phenotypic ratio would be 9 dominant : 3 heterozygous : 4 recessive.
Step-by-step explanation:
The expected phenotypic ratios in the offspring of two horses that are both heterozygous for both traits can be determined using a Punnett square. Let's say one trait is represented by the letter A (with dominant allele A and recessive allele a) and the other trait is represented by the letter B (with dominant allele B and recessive allele b). In this case, the genotypes of the parent horses would be AaBb. When crossbreeding these horses, the possible genotypic ratios in the offspring can be determined by filling out the Punnett square. For each trait, you will have three genotypes: homozygous dominant (AA), heterozygous (Aa), and homozygous recessive (aa). The phenotypic ratios would depend on the dominance relationships between the alleles for each trait. Let's assume that in this case, both A and B alleles are dominant. In that case, the expected phenotypic ratio in the offspring would be 9 dominant : 3 heterozygous : 4 recessive.