In a heterozygous animal, the dominant trait takes over. For example, if black is dominant, that animal will have black fur. If two alleles have incomplete dominance, neither one will show full dominance over another, and a heterozygous (black and white) animal would have gray fur, intermediate between the two alleles. In codominance, both alleles are dominant, so a heterozygous black and white animal would have mottled fir of both colors.