This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Haematology, Subject name: Anatomy
Which of the following is not seen on hemoglobin electrophoresis in sickle cell anemia 
Select and explain. 
A. HbA, B. HbA2, C. HbF, D. HbS
A: HbA
Answer: A: HbA 
Explanation: Ref Harrison 19 th ed pg 634 sickle cell syndromes are caused by a mutation in the b-globin gene that changes the sixth amino acid from glutamic acid to valine. HbS (a2 b2 6 Glu-Val) polymerizes reversibly when deoxygenated . No beta chains and therfther no HbA