Sickle cell anemia is a hereditary disorder of autosomal nature. This is an autosome linked recessive trait that can be transmitted from parents to the offspring when both the partners are carriers for the gene (or heterozygous). The disease is controlled by a single pair of alleles, HbA and HbS. Out of the three possible genotypes, only homozygous individuals for HbS (HbS HbS) show the diseased phenotype. It is caused by a mutation of the gene controlling β− chain of haemoglobin. It involves substitution of glutamine by valine.