Fetal hemoglobin (HbF\text{HbF}HbF) is the main oxygen transport protein in human fetuses, but its production normally ceases shortly after birth, replaced by adult hemoglobin (HbA\text{HbA}HbA). Some adult humans continue to produce fetal hemoglobin, a condition known as Hereditary Persistence of Fetal Hemoglobin (HPFH). This trait is controlled by a dominant allele. In regions where severe malaria is endemic, individuals with HPFH show increased survival rates because HbF\text{HbF}HbF restricts malaria parasite development.
Describe how the presence of malaria as a selective pressure could have led to an increase in the frequency of the HPFH trait in certain populations.
Explain why the proportion of individuals showing the HPFH phenotype would rapidly increase in a population once selection for this condition had been established.
HPFH can be caused by a point mutation in the regulatory DNA. This mutation does not occur within the protein-coding sequence of the γ\gammaγ-globin gene (the gene representing the fetal hemoglobin subunit).
Suggest and explain how this mutation causes HPFH.
