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The gene associated with sickle cell anemia is HBB, which is located in region 15.5 on the short arm of chromosome 11. There are many variations that can cause sickle cell, but primarily it is caused by the hemoglobin variant Hb S. According to the human genome project website: "the hydrophobic amino acid valine takes the place of hydrophilic glutamic acid at the sixth amino acid position of the HBB polypeptide chain. This substitution creates a hydrophobic spot on the outside of the protein structure that sticks to the hydrophobic region of an adjacent hemoglobin molecule's beta chain. This clumping together (polymerization) of Hb S molecules into rigid fibers causes the "sickling" of red blood cells." In a nutshell, when the hydrophobic (water fearing) amino replaces a hydrophilic one (water loving) on the protein chain, it creates a spot that sticks to another similar mutated gene, and they clump together, creating a sickle shaped cell. Looking at the location and incidence rates of sickle cell amenia, scientists believe that because malaria rates are high in the region, the body has created this defense against the disease -- an evolutionary self defense. Hope that helps :-)

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16y ago

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