Question

At birth, blood cells stop producing fetal hemoglobin and start producing adult hemoglobin. What do you think might happen if a newborn fails to make this switch?

a. The newborn will not survive.

b. Hemoglobins will not become saturated with oxygen.

c. Actively metabolizing tissues may not obtain enough oxygen.

d. There will be a lower oxygen reserve in the body.

e. There will be no major effect to the newborn.

Answer 1

Answer: e. There will be no major effect to the newborn

Explanation:

In the fetus, haemoglobin is a tetramer made of two alpha globin cubuints and two gamma globin subunits. It has a high affinity to oxygen and is hence produced in the groing fetus to allow the fetus to take up the oxygen from maternal blood. After birth, the levels of fetal haemoglobins gradually decrease and within a year after birth, are mostly replaced by adult haemoglobin (with only 1% fetal haemoglobin persisting in adulthood).

This condition where the switch from fetal to adult haemoglobin fails due to a mutation (in the promoter region of HBG1 and HBG2) is called Hereditary persistence of fetal hemoglobin (HPFH). In such a case, the levels of fetal haemoglobins can be around 26-28% in adulthood. However, this condition presents in symptoms by itself. It usually remains asymptomatic. Complications might arise only when other haemoglobin related disorders are also present.

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