Sickle cell anemia results from a mutation in the gene that makes hemoglobin, the iron-rich compound in red blood cells. Hemoglobin enables red blood cells to carry oxygen from the lungs throughout the body. The hemoglobin associated with sickle cell anemia causes red blood cells to become rigid, sticky, and misshapen. For a child to be affected, both parents must carry one copy of the sickle cell gene, and both mutated copies must be passed on to the child. If only one parent passes on the sickle cell gene to a child, that child becomes a carrier of sickle cell anemia. With one typical hemoglobin gene and one mutated form of the gene, individuals with sickle cell trait produce both typical hemoglobin and sickle hemoglobin.