Sickle-cell anemia is a genetically inherited disease. Homozygous individuals (SS) have normal blood cells that are easily infected with the malarial parasite. Thus, many of these individuals become ill and may die. Individuals homozygous for the sickle-cell trait (ss) have sickled red blood cells that readily collapse when deoxygenated. Although malaria cannot grow in these red blood cells, individuals often die because of the hemoglobin disorder. However, individuals with the heterozygous condition (Ss) have some sickling of red blood cells, but generally not enough to cause death. In addition, the heterozygotes tend to survive better than either of the homozygous conditions as they are resistant to malaria.

Question:
Sickle cell anemia or sickle cell disease is caused by a genetic mutation. Describe the mutation at the DNA level. Explain the effects at the protein level.