HbF

2,3-DPG binds the beta subunits, so the form of hemoglobin that has the least beta subunits will be most similar to a mutated beta subunit =======> 2,3-DPG binds beta subunits after hemoglobin has been deoxygenated. Fetal hgb binds oxygen with higher affinity due to its inability to interact with 2,3-DPG