6. Sickle cell anemia is a genetic disease that is most common in people from the malaria belt of Africa. The disease results from a mutation in the hemoglobin gene, which causes the red blood cells to collapse easily into a cushion shape. These sickle cells cause clots, which result in many physiological problems. Malaria in this region is from the species P. falciparum, which is highly virulent and often fatal. In fact, 3000 children die per day from malaria in that region (about 1 million per year). Heavy selection pressure by malaria is theorized to have established a mutant allele, the sickle cell allele, in people of the malaria belt of Africa. The sickle cell allele is thought to convey resistance to malaria; unfortunately, it is known to be a recessive lethal (death in early childhood). Allison and Clyde tested young children from the malaria belt of Africa for the sickle cell allele and the severity of malaria. The sickle cell allele is denoted Hbs and the normal allele HbA. Heavy Light Total Infection Infection Hbs HbA HbA HbA 36 100 136 152 255 407 Total 188 355 543 Test the model (chi-square test) that the genotype-defined populations differ in the intensity of malaria infection.

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