What is the cause of sickle cell trait?

It is inherited: Hemoglobin (HGB) is a complicated chemical that is in the red blood cells and carries oxygen. We inherit one gene from each parent that makes one of the parts of HGB called beta chains. If we inherit a sickle beta chain gene from one parent and a normal beta chain gene from the other, we have sickle trait. If we inherit a sickle beta chain gene from both parents, we have sickle cell anemia.

Mutated gene: It is believed a single gene mutation occurred hundreds of years ago in a person in sub-Saharan Africa. When carried as one of a pair (trait), it seemed to confer resistance to malaria. It is transmitted as a recessive gene, meaning the normal gene next to it can do the work. When 2 defective genes are present, (sickle cell disease) the proper work is not done and the blood cells are defective.