Which of these is true of fetal haemoglobin?

Hb F binds less avidly to 2,3 DPG than HbA and thus has higher affinity for oxygen than HbA Almost 65 to 90% of haemoglobin at bih is HbF. After bih HbF gamma gene is switched off and HbA beta gene is switched on so more and more HbA is formed. Sickle cell patients have relatively high amounts of fetal Hb. HbA first appears in fetal blood at 11 weeks when bone marrow stas hematopoesis Remember: The fetal hemoglobin stas appearing at 11 weeks, but the 'Switch - Over' from Fetal hemoglobin's utilisation for oxygen transpo to Adult haemoglobin for oxygen transpo happens at 30-32 weeks...