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BIOL 207 (09/20/13) Lec. 6: Causes of Gene Mutation (con't) & Lec. 7: Consequences of Gene Mutation

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Biology (Biological Sciences)
Mike Harrington

BIOL 207 (September 20, 2013) Lecture 6: Causes of Gene Mutation (con’t) | Lecture 7: Consequences of Gene Mutation Examples of Induced Gene Mutations a. EMS (Ethyl methanesulphonate)  Binds to Guanine and makes it alters its appearance (G*) to make it look like Adenine i. G + EMS = G*  appears to be A  Possible happenings: b. Tobacco Smoke  A metabolic derivative of benzo[a]pyrene binds to ‘G’ i. Note that this is NOT a mutation 1. Something is clearly wrong with the sequence 2. BUT the sequence is still the same (= no mutation)  G + M.D of benzol[a]pyrene = G* i. G* is not recognized by DNA polymerase ii. Resulting sequence of occurrences: c. Gamma Rays and X-Rays  Causes double-stranded DNA breaks i. If there is only one break in the DNA, it gets fixed no problem ii. The existence of telomeres allows NHEJ proteins to know which end goes with which end and repairs the break. 1. NHEJ = non-homologous end-joining system  Problems arise when: i. There is more than on break in a nucleus’s DNA ii. Possible outcomes: 1. Deletions (pieces of DNA sequence cut out) 2. Inversions (pieces of DNA on the same chromosome switch places) 3. Deletions followed by duplications (shortened DNA strand length is “remedied” by the replication of a segment of DNA)
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