Sickle Cell Anemia is a kind of typical blood disease showing autosomal recessive character and it can be characterized by chronic anemia and periodic pain attacks. The disease arises from amino acid replacement within the protein structure of an oxygen carrying molecule, hemoglobin, where glutamic acid is replaced by valine (HbS).
After this genetic defect happens, spherical or ball-shaped normal hemoglobin looks rather like a sickle under certain circumstances like oxygen deficiency that ultimately causes a reduction in oxygen binding and carrying ability of Hb.