Sickle cell anemia
occurs when someone has 2 sickle cell genes.
Normal hemoglobin (hb) genes code for hb a. A sickle cell gene codes for hb s. Having 1 hb a gene & 1 hb s gene leads to sickle trait. This will have no symptoms, but has some health consequences. 2 genes for hb s leads to sickle cell anemia. To make things more complicated, there are other abnormal hb genes that can cause problems.