the mutation that results in sickle cell anemia is
Sickle-cell disease Normally, humans have haemoglobin A, which consists of two alpha and two beta chains, haemoglobin A2, which consists of two alpha and two delta chains, and haemoglobin F, consisting of two alpha and two gamma chains in their bodies. Out of these three types, haemoglobin F dominates until about 6 weeks of age. Afterwards, haemoglobin A dominates throughout life.[citation needed] In people diagnosed with sickle cell disease, at least one of the β-globin subunits in hemoglobin A is replaced with what's known as hemoglobin S. In sickle cell anemia, a common form of sickle cell disease, hemoglobin S replaces both β-globin subunits in the hemoglobin.[15]