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Lecture 6 04

Lecture 6 04 - Lecture 6 Thursday-1 Announcements Tests In...

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Lecture # 6 – Thursday, 4/17/08 - 1 - Announcements: - Tests. In the last few years of the class, grades have been based solely on a final test. But we’re going to keep the format of the class the way it is. - Genetic Nomenclature . Q. In cases of familial cancer syndromes , tumor suppressor genes (TSG) act in an autosomal dominant fashion, but cells need a second hit mutation to induce the malignant phenotype? How can it be autosomal dominant but need a second hit? If it’s a dominant mutation, isn’t it dominant already?? A. The autosomal dominant part as a malignant tumor phenotype refers to the organism/individual as a whole, not the cell. The phenotype is getting cancer, and that will act in the context of a single mutant on one allele of the TDG. In cell, takes 2 nd hit to get there. Phenotype is apparent in the individual, but not in cell. Each cell in the individual’s body will inherit the mutation in an autosomal dominant fashion. But in each cell itself, the mutated (tumor suppressor) gene’s effect on malignancy acts more in a recessive fashion. To diagram it out, No mutations = +/+ where + = non-mutated gene Familial cancers = +/- where - = mutated gene Malignancy = -/- So in familial cancer syndromes, every cell has inherited the first mutation in the tumor suppressor gene (heterozygous), but malignancy requires homozygosity of the mutated gene. And this is because the presence of a functional version of the gene can compensate the lack of a functional gene. Today’s lecture – continue TSG discussion. Tumor Suppressor Genes can be categorized into 2 groups, functions along one of these two lines 1. Gatekeeper TSG’s – act to control cell proliferation and arrest aberrant proliferation; important gene in cell cycle control Ex. Rb gene 2. Caretaker TSG’s – responds to DNA damage and other insults to the cell, induces growth arrest or apoptosis; steps in when cells are damaged to either stop cell from continuing in the cell cycle or apoptose. Ex. p53 BE CAREFUL to KEEP IN MIND these ideas: - Dominance vs. Recessiveness - Organism vs. Cell - Put things in context Is the malignant phenotype dominant or recessive at the cellular level? Experiment: Cell Fusion - Put two different cells next to each other w/ electrodes on either end and pulse an electric shock across them.
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Lecture # 6 – Thursday, 4/17/08 - 2 - - Their cell membranes will be disrupted and then fuse, sometimes even nuclei fuse. - Can made one big cell with two nuclei and ask which phenotype takes over as a result. Put in context: Fuse a malignant cell and a non-malignant cell, which one will the fused cell become malignant or non-malignant? If you have a malignant cell and a non malignant cell, which one rules??? Q. Wouldn’t it depend on the health of the non-malignant cells?
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Lecture 6 04 - Lecture 6 Thursday-1 Announcements Tests In...

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