The disorder is caused by a genetic mutation in the HBB gene, which provides instructions for making the beta-globin subunit of hemoglobin. The specific mutation responsible for sickle cell anemia is a point mutation, where a single nucleotide change results in the substitution of the amino acid valine for glutamic acid at position 6 of the beta-globin chain. This altered form of hemoglobin is known as hemoglobin S (HbS).
