An individual who displays the disease sickle-cell anemia must have inherited the deleterious allele from both phenotypically normal parents. what, therefore, is this individual?

I think the individual is therefore homozygous recessive. Sickle cell anemia is a disorder of the blood caused by an inherited abnormal hemoglobin. The abnormal hemoglobin causes distorted red blood cells. The sickle red blood cells are fragile and prone to rupture. Sickle cell anemia is as a result of mutation in a single gene (β-thalassemia).