Session 17 (Molecular Biology and Medicine)

Session 17 (Molecular Biology and Medicine) - MCB 181 Study...

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MCB 181 Study Session 17 (Molecular Biology and Medicine) Proto-oncogenes encode for normal cellular proteins involved in growth signalling pathways. When these genes become mutated as a result of exposure to chemicals, radiation, or other carcinogens, these genes are called oncogenes.
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Learning Goals for Study Session 17 (Molecular Biology and Medicine) Briefly describe how point mutations lead to diseases and disorders such as PKU, Sickle-cell disease, cystic fibrosis, FH, and hemophilia. Describe the screening technique for PKU and indicate how knowledge of the disorder was used to developed the technique. Be able to describe the types of genetic changes that occur in cancer, the major difference between benign and malignant tumors, and the relationship between oncogenes and tumor suppressor genes.
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Molecular Biology and Medicine In the previous study session we considered the techniques that are available to isolate and manipulate genes. Here we focus on how our knowledge of molecular biology has been used to study, understand, diagnose and treat human diseases and disorders. We begin by considering several examples of how a point mutation in a gene leading to an abnormal protein causes serious human diseases.
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Phenylketonuria (PKU)- A single gene recessive trait caused by a point mutation leading to an abnormal enzyme! Homozygous recessive individuals (1 in 12,000 births in U.S.) have a non-functional enzyme (phenylalanine hydroxylase) in the liver for the conversion of phenylalanine to tyrosine. An excess of phenylalanine in the blood leads to accumulation of toxic phenylpyruvic acid. If not treated with a low phenylalanine diet, individuals exhibit severe mental retardation. The defect in the enzyme consists of one amino acid change (tryptophan instead of arginine) at position 408 in the 451 amino acid polypeptide. The enzyme is made, it just doesn’t function properly. This allele resulted from a point mutation in the gene coding for the enzyme. Heterozygous individuals produce sufficient amounts of normal enzyme to show no symptoms. Without early detection and changes in diet, homozygous recessive individuals are at risk for severe mental retardation.
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Sickle-cell disease - A single gene recessive trait caused by a point mutation leading to abnormal hemoglobin! Sickle-cell disease is the most common
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This note was uploaded on 03/24/2010 for the course MCB 181 taught by Professor Jorstad during the Spring '07 term at University of Arizona- Tucson.

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Session 17 (Molecular Biology and Medicine) - MCB 181 Study...

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