Affinity of Hemoglobin-F for oxygen is more than Hemoglobin-A for which of the following reason?

Answer: d) 2,3 DPG poorly binds to fetal HB.* Under physiologic conditions, Hb F has a higher affinity for oxygen than does Hb A, as a result of Hb F binding only weakly to 2,3-BPG.* The y-globin chains of Hb F lack some of the positively charged amino acids that are responsible for binding 2,3-BPG in the P-globin chains.* Because 2,3-BPG serves to reduce the affinity of hemoglobin for oxygen, the weaker interaction between 2,3-BPG and Hb-F results in a higher oxygen affinity for Hb F relative to Hb A.* In contrast, if both Hb A and Hb F are stripped of their 2,3-BPG, they then have a similar affinity for oxygen.