here is a benign congenital condition called Hereditary Persistence of Fetal Hemoglobin (HPFH) in which production of the fetal hemoglobin (HbF) is not switched off post-partum (after birth). It is due to a mutation in the β-globin gene cluster. People that are homozygotes for this mutation, meaning that the gene from both parents is mutated, continue to make almost exclusively HbF throughout their life rather than adult hemoglobin (HbA). HPFH homozygotes demonstrate a slight erythrocytosis, or an increase in the number or mass of their red blood cells, and consequently an increase in the concentration of HbF. Given only what you know about the oxygen saturation dynamics of HbF versus HbA, can you explain why there might be the slight erythrocytosis in HPFH homozygotes?
There is a benign congenital condition called Hereditary Persistence of Fetal Hemoglobin (HPFH) in which production of the fetal hemoglobin (HbF) is not switched off post-partum (after birth). It is due to a mutation in the β-globin gene cluster. People that are homozygotes for this mutation, meaning that the gene from both parents is mutated, continue to make almost exclusively HbF throughout their life rather than adult hemoglobin (HbA). HPFH homozygotes demonstrate a slight erythrocytosis, or an increase in the number or mass of their red blood cells, and consequently an increase in the concentration of HbF. Given only what you know about the oxygen saturation dynamics of HbF versus HbA, can you explain why there might be the slight erythrocytosis in HPFH homozygotes?
It has been observed that the prevalence of HPFH is much higher in populations with certain hemoglobinopathic disorders such as sickle cell anemia, and is selected for in populations with a high prevalence of these conditions, which in turn are often selected for in areas where malaria is endemic due to the protective effect of sickle cell anemia against malaria. If HPFH does not directly confer protection against malaria, and without knowing anything further about the molecular pathogenesis of sickle cell anemia, can you speculate why it would be so prevalent in people with sickle cell anemia?
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