TAILIEUCHUNG - Lecture Biology - Chapter 17: Genome sequencing, molecular biology, and medicine

Lecture Biology - Chapter 17: Genome sequencing, molecular biology, and medicine. The topics discussed in this chapter are: How do defective proteins lead to diseases? What kinds of DNA changes lead to diseases? How does genetic screening detect diseases? What is cancer? How are genetic diseases treated? What have we learned from the human genome project? | Genome Sequencing, Molecular Biology, and Medicine 17 Genome Sequencing, Molecular Biology, and Medicine How Do Defective Proteins Lead to Diseases? What Kinds of DNA Changes Lead to Diseases? How Does Genetic Screening Detect Diseases? What Is Cancer? How Are Genetic Diseases Treated? What Have We Learned from the Human Genome Project? How Do Defective Proteins Lead to Diseases? Genetic mutations are often expressed as proteins that differ from wild-type. Genetic diseases can result from abnormalities in enzymes, receptor proteins, transport proteins, structural proteins, etc. How Do Defective Proteins Lead to Diseases? Phenylketonuria (PKU) was traced to its molecular phenotype in the 1950s. Results from an abnormal enzyme phenylalanine hydroxylase—normally catalyzes conversion of dietary phenylalanine to tyrosine. The abnormal enzyme has tryptophan instead of arginine in position 408. Figure One Gene, One Enzyme How Do Defective Proteins Lead to Diseases? People with PKU have light skin and hair color. Melanin—pigment in dark skin and hair, is made from tyrosine, which people with PKU can not synthesize. How Do Defective Proteins Lead to Diseases? Polymorphism in proteins does not always mean disease. There can be numerous normal alleles of a gene which produce normally functioning proteins. How Do Defective Proteins Lead to Diseases? The first human disease known to be caused by an abnormal protein was sickle-cell disease. The abnormal allele produces abnormal hemoglobin that results in sickle-shaped blood cells. The sickle-shaped cells block blood flow in capillaries. How Do Defective Proteins Lead to Diseases? Hemoglobin—protein with quaternary structure; 2 α and 2 β chains. In sickle-cell disease, one of 146 amino acids in the β-globin chain is different: glutamic acid (negatively charged) is replaced by valine (neutral). Changes shape of the hemoglobin and causes anemia. Do Defective .

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