10781 - Sickle cell anemia and thalassemias Paul R. Earl...

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Sickle cell anemia and  thalassemias Paul R. Earl Facultad de Ciencias Biológicas Universidad Autónoma de Nuevo León San Nicolás, NL, Mexico  pearl@dsi.uanl.mx
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  Genetic explanations.   Thalassemia is caused by  impaired production of either the  α  or  β  hemoglobin chain. Alpha  ( α ) thalassemia occurs when one  or more of the 4 alpha chain genes  fails to function.  
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A ) The loss of one gene  diminishes the production of the  alpha protein only slightly. This  condition is so close to normal  that it can be detected only by  specialized laboratory  techniques. A person with this  condition is called a silent carrier  because of the difficulty in  detection. 
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B ) The loss of 2 genes (2-gene  deletion alpha ( α ) thalassemia)  produces a condition with small  RBCs, and at most a mild anemia.  People with this condition look and  feel normal. The condition can be  detected by routine blood testing,  however. 
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C)   The loss of 3 alpha genes produces a  serious hematological problem (3-gene  deletion  α  thalassemia). Patients with this  condition have a severe anemia, and often  require blood transfusions to survive. The  severe imbalance between the alpha chain  production (now powered by one gene,  instead of 4) and beta chain production  (which is normal) causes an accumulation  of beta chains inside the RBCs. Normally,  beta chains pair only with alpha chains.  
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D ) The loss of all 4 alpha genes  during fetal life causes death  in  utero  or shortly after birth. Rarely,  4 gene deletion alpha  thalassemia has been detected  in  utero , usually in a family where  the disorder occured in an earlier  child. Repeated transfusions can  keep victims alive. 
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E ) There are 2 genes for the beta  chain of hemoglobin in  β - thalassemia. Unlike  α -thalassemia,  β -thalassemia rarely arises from  the complete loss of a beta globin  gene that is present, but produces  little beta globin protein. The types  of genes can be analyzed in each  case.
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This note was uploaded on 02/23/2012 for the course PHARM 290 taught by Professor Staff during the Fall '10 term at Rutgers.

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10781 - Sickle cell anemia and thalassemias Paul R. Earl...

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