Text: Hemoglobin is a protein that is carried by red cells. It picks up oxygen in the lungs and delivers it to the peripheral tissues for metabolism. Hemoglobin molecules are actually an assembly of 4 protein subunits (2 alpha polypeptides and 2 beta polypeptides). .

Like all proteins, the "blueprint" for hemoglobin exists in DNA (the material that makes up genes). Normally, an individual has four genes that code for the alpha protein, or alpha chain. Two other genes code for the beta chain.