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Chemistry Applications Essay Sickle Cell Anemia Sickle cell anemia is an autosomal recessive genetic blood disorder that occurs when hemoglobin molecules are abnormal or the person does not have enough red blood cells. Hemoglobin is a complex iron-rich protein with a quaternary structure in our blood that carries oxygen from the lungs to other parts of the body. Sickle cells are sticky and stiff. Sickle cell anemia is hereditary and is often passed on from one generation to the next. It usually causes a decreased life span. When someone has sickle-cell anemia their hemoglobin molecules have a lower solubility, especially in their unoxygenated form. The insolubility of the hemoglobin is caused by the structural change in one part of the amino acid chain. When hemoglobin is normal the amino acid‘s side chain that protrudes from the main body terminates in a polar group. The polar side chain contributes to the solubility of the hemoglobin molecule in the water throughout the body. When someone has sickle cell anemia their side chain differs. Instead of being polar, hydrophobic, the abnormal groups of atoms are nonpolar making it hydrophobic, water fearing. This is caused by a gene defect, a mutation of one nucleotide from Uracil to Adenine, which results in valine to substitute glutamic acid. Since this occurs in their hemoglobin it leads to clump into hemoglobin particles that are too large to stay suspended in biological fluids. The cell distorts into a sickled shape and it tends to clog the capillaries which deprives the downstream tissues of oxygen and causes infarction and ischemia. Sickle cell also causes physical weakness, severe pain, stroke, and the gradual deterioration of the vital organs. It also raises the risk for infection. More than 70,000 Americans have sickle cell anemia. Also, about two million Americans are carriers of the trait. Since the allele responsible for sickle cell anemia is autosomal recessive, when two parents are heterozygous carriers, their child has a 1-in-4 chance of having the disorder and a 1-in-2 chance of being a carrier, like their parents. A carrier is a person that receives one defective and one healthy allele from their parents. These people remain healthy, but can pass the disorder to their offspring. These carriers are relatively resistant to malaria because have some sickled red blood cells, but not enough to cause symptoms. This is good in some parts of the world because the malaria parasite spends part of its complex life cycle in red blood cell. In those that are heterozygous, the presence of the malaria parasite causes the red blood cell to rupture, which makes the plasmodium unable to reproduce. Since being heterozygous is considered favorable in parts of the world such as Africa, India, the Middle East, and the Mediterranean because of its relative resistance from malaria the illness is still prevalent. This heterozygote advantage is due to heterozygotes higher fitness.

Works Cited //**“TeensHealth.”**// The Nemours Foundation, September 2012. Web. 3 January 2013.
 * //“National Heart Lung and Blood Institute.”//** [|National Institutes of Health] //and// [|Department of Health and Human Services] //, 28 September 2012. Web. 3 January 2013.//