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Hemoglobin and Porphyrins Objectives

Produces a disorder called thalassemia minor which is

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produces a disorder called thalassemia minor which is clinically asymptomatic and resembles iron deficiency; the homozygous state, thalassemia major, is usually lethal before birth or in childhood) ALPHA THALASSEMIA--- 2 alpha genes are located on each chromosome 16, 1 inherited from the mother and the other from father yielding a total of 4 alpha genes; it occurs mostly in Asian, African, and African American populations; Hydrops fetalis – most clinically severe form---Increase in Hg Bart – very high affinity for O2 – no O2 transport to tissues – stillborn or death shortly after birth; Hg H disease---have an alpha chain synthesis about 1/3 of beta chain synthesis which results in the beta chains accumulating and forming tetramers which are called hemoglobin H---beta chain precipitates (hg h inclusions) alter shape and ability of the cell to deform significantly shortening the lifespan of the cells---individuals have moderate hemolytic anemia; Minor – Silent Carriers---missing only 1 alpha gene BETA THALASSEMIA--- a large majority of the defects results from point mutations; Homozygous beta thalassemia (major) – crippling disease of childhood – hypochromic, normocytic anemia; structural bone abnormalities; Heterozygous beta thalassemia (minor) – usually asymptomatic; could have microcytic anemia, basophilic stippling, target cells 9. Explain the basic principles of the following methods: solubility testing, hemoglobin electrophoresis pg. 437-438. Solubility test is usually a screening test while electrophoresis is confirmatory. SOLUBILITY TEST--- sickling hg (Hg S) in the deoxygenated state is relatively insoluble and forms a precipitate when placed in a high molarity phosphate buffer solution; the precipitate forms because the deoxygenated hg forms tactoids that refract and deflect light rays, producing a turbid solution; the sample is placed about 1 inch in front of a heavy, black lined index card; if there is no sickling hg present the lines will be visible; if there is sickling hg present the lines will be indistinct or impossible to read CELLULOSE AGAR HEMOGLOBIN ELECTROPHORESIS--- performed on a cellulose acetate plate at a pH of 8.4-8.6; a rough estimate of proportions of diff hg may be made using a densitometer; the order of electrophoresis mobility from slowest to fastest is Hgs C,S,F, and A (Accelerated, Fast, Slow, Crawl) CITRATE AGAR ELECTROPHORESIS--- performed at a pH of 6.0-6.2 after abnormal Hg is determined on cellulose agar electrophoresis; in this method an important
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Hemoglobin and Porphyrins – Objectives method in determining the mobility of Hg is solubility; Hg S and Hg C are rather insoluble.
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