Sickle-cell anemia is an example of codominance. What implications does this have for people with one or two copies of the sickle-cell gene?

Sickle cell anemia is a genetical disorder that occurs when both the alleles from both the parents in the offspring is recessive. If only one gene is recessive, then the person will not have the disease.

It is a disease in which the shape of the red blood cell alters from biconcave disc shape to sickle shaped because of the mutation in hemoglobin gene. It is a case of incomplete dominance in which for the disease to occur, both the genes have to be recessive.