When does switchover from fetal to adult hemoglobin synthesis begin –

Fetal Hb → (α2 γ2) Adults Hb → (α2 β2) During the initial fetal life, the major haemoglobin synthesized in the body is fetal haemoglobin, because, in the fetus, the chain synthesized predominantly is the γ chain. the β chain is present in only trace amount in early embryos The rate of synthesis of y and β chains and the amount of HbA and HbF are inversely related during the intrauterine stage. As the age of the fetus increases, the synthesis of β chains and the amount of adult haemoglobin in the blood increases At 36 weeks of gestational age the rate of synthesis of (β chain exceeds that of γ chain. This is called switch over.