In codominant inheritance, both alleles are expressed equally in the phenotype of the offspring. In this case, the alleles for coat color are represented as:
- CWCW for white
- CBCB for black
When you breed these two homozygous horses, the offspring will inherit one allele from each parent. Therefore, all offspring will have the genotype CWCBC, where both the white and black alleles are present.
Given that this gene follows a codominant inheritance pattern, the phenotype of the offspring will be roan, which represents both colors in the hair.
Thus, the likelihood that the offspring will be roan is 100%.
Answer: 100%