What is the cause of sickle cell disease and trait?

Gene mutation: Sickle cell trait is caused bu the presence of a single mutation in the beta chain of human hemoglopin a gene. A mutation in one gene on one of a person's two beta globin genes results in sickle cell trait (sa hemoglobin) while the same mutation in both of a persons genes causes sickle cell anemia. (ss hemoglobin). The term trait means a carrier for the sickle cell mutation.