A

Replacing negatively charged glutamic acid with neutral valine removes a negative charge from the β-globin chain, so HbS carries a less negative net charge than HbA. On alkaline gel electrophoresis (migration toward the anode), the less negatively charged HbS moves more slowly, giving it decreased electrophoretic mobility relative to normal hemoglobin [Murayama, 1966, PMID 5940355; Mandal, 2020, PMID 32189305].