Sickle cell anemia is an inherited disease. People who have the disease inherit two genes for sickle hemoglobin, one from each parent. Sickle hemoglobin causes red blood cells to develop a sickle, or crescent, shape. Sickle cells are stiff and sticky. They tend to block blood flow in the blood vessels of the limbs and organs. Blocked blood flow can cause pain and organ damage. It can also raise the risk for infection. The gene defect is a known mutation of a single nucleotide (A to T) of the β-globin gene, which results in Glutamic acid being substituted by Valine at position 7. The genetic disorder is due to the mutation of a single nucleotide, from a GAG to GTG codon on the coding strand, which is transcribed from the template strand into a GUG codon.