Phenylketonuria and Galactosemia

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1.Phenylketonuria (PKU). 1.1. History Phenylketonuria was discovered by the Norwegian physician Ivar Asbjørn Følling in 1934 when he noticed that hyperphenylalaninemia (HPA) was associated with mental retardation (Phenylketonuria, n.d.). In Norway, this disorder is known as Følling's disease, named after its discoverer (Phenylketonuria, n.d.). Dr. Følling was one of the first physicians to apply detailed chemical analysis to the study of disease (Phenylketonuria, n.d.). His careful analysis of the urine of two affected siblings led him to request many physicians near Oslo to test the urine of other affected patients (Phenylketonuria, n.d.). This led to the discovery of the same substance that he had found in eight other patients (Phenylketonuria, n.d.). The substance found was subjected to much more basic and rudimentary chemical analysis (taste) (Phenylketonuria, n.d.). He conducted tests and found reactions that gave rise to benzaldehyde and benzoic acid, which led him to conclude the compound contained a benzene ring (Phenylketonuria, n.d.). Further testing showed the melting point to be the same as phenylpyruvic acid, which indicated that the substance was in the urine (Phenylketonuria, n.d.). His careful science inspired many to pursue similar meticulous and painstaking research with other disorders (Phenylketonuria, n.d.). 1.2. Causes Phenylketonuria (PKU) is an inherited, autosomal recessive disorder (Letcher, 2002). It is caused by alterations or mutations in the genetic code for the phenylalanine hydroxylase (PAH) enzyme (Letcher, 2002). Mutations in the PAH gene prevent the liver from producing adequate levels of the PAH enzyme (Letcher, 2002). This enzyme phenylalanine hydroxylase is required to convert the amino acid phenylalanine into amino acid tyrosine (Letcher, 2002). If this reaction does not take place, phenylalanine accumulates and tyrosine

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