An Examination of the HBB Gene in Various African Populations
Malarial resistance serves as a prime example of how infectious disease and parasite loads have affected human evolutionary biology. Claiming over 1 million deaths worldwide every year, malaria's wide and severe effects on the human condition are undeniably strong. However, studies on populations existing in malaria endemic areas have revealed numerous biological adaptations that confer resistance against the disease. Major forms of genetic resistance to malaria are seen through variants involved in sickle cell disease, Duffy blood antigens, glycophorins, blood type groupings, and glucose-6-dehydrogenase deficiency. Of these the best studied are the genetic variants in the HBB gene, which is responsible for the construction of hemoglobin in erythrocytes. Variants of the HBB gene include HbS, HbC, HbE, and variants involved in beta-thalassemias, which are present at varying frequencies in different areas of the world in response to the pressure of malarial disease. African populations in particular are of great interest due to their greater genetic diversity and the high rates of malarial diseases reported in African countries. As such, sequencing the genotypes of multiple African populations would give a greater understanding to the frequencies of the two major HBB variants present in Africa, HbS and HbC. Furthermore, given the strong selective pressure an infectious disease such as malaria would place on populations in malaria-endemic regions, it is possible that multiple variants may have evolved in these populations in attempt to combat the disease. By sequencing the HBB gene and its corresponding upstream region in 260 individuals from 15 different African populations, the frequencies of the HbS and HbC SNPs have been determined.