Codominance — Overview & Examples

Sickle cell anemia is transmitted via recessive alleles. Two recessive alleles are necessary for the disease to appear. However, the way the allele affects blood cell shape works differently. Having one sickle cell allele is enough to make some blood cells be sickle shaped. There are enough normal blood cells to prevent anemia from forming.

If actually developing sickle cell anemia is through dominant/recessive methods of inheritance, what is the method of inheritance for the actual formation of sickle cells?