Lecture 25 - Lecture25

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oncogene is a gene that causes cancer, causes the cell to have unregulated cell divi- sion. Carcinogen vs mutagen mutagen - any agent that damages DNA Carcinogen - chemical agent that increases the risk of getting cancer. one of the mechanisms of getting cancer is by DNA damage. rate of cancer is proportional to your age at a linear fashion. One cell in the entire body accumulates the right amount of mutations, clonally di- vides to produce a tumor then metastasizes to all parts of the body, if you get rid of the single cell before it gets loose then there wouldn’t be any problems. The more you divide the greater chance you have to mutate the reason mutagens increase the chances of DNA damage is if you have UV or some intercalating agent, the polymerase makes a mistake at a higher rate. And so having car- cinogens just make the DNA polymerase more error prone, obviously things that eliminate DNA repair make the chances of error of natural metabolism even higher. Cancer is caused by the inappropriate expression of either dominant mutant oncogen- esis and the elimination of recessive tumor suppressor genes (TSGs) The definition of an oncogene is something that results in oncogenesis which means cancer, since you have two copies of every autosomal gene; if you have one wild type copy and one mutant copy you still get cancer because the function of these genes are positive stimulators of cell division they are telling the cell to divide. They usually tell in the absence of environmental cues that would tell it to divide under the proper circumstances. Normally your cells can divide, but they divide when your an embryo, growing, or when you have a wound and stops when you don’t need division to occur. What a cancer cell does it just keeps dividing and is immune to the constraints. On- cogenic mutations are dominant to the wild type because if one gene is off and say- ing not to divide while the other gene is saying to divide, the wild type gene cannot stop the gene saying to divide. Have other types of genes called tumor suppressor genes, these are the genes that are check points they regulate the cell so that incorrect division does not occur. TSGs stop this division and mutation in TSGs are recessive because if if you have one wild type copy telling the cell not to divide then the other mutant copy that is eliminating that func- tion will not cause the cell to divide. Tumors are masses of cells derived from a single cell cancer progress from single mutant cell that on average sequenctially accumulates seven different mutations. the reason that cancer is age dependent is that the cells are clonal. to a tumor cell
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This note was uploaded on 01/26/2009 for the course BIOLOGY 244 taught by Professor Palter during the Fall '05 term at Temple.

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Lecture 25 - Lecture25

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