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I. Mutations: what are they?A. They are changes in the DNA sequenceB. Can arise:C. Consequences of mutations in a haploid genome:D. If mutation is not repaired before next round of replication:E. Revision to wild-type is possible depending on the nature of the mutationII. Types of Mutations:A. Single base pair mutations (called a substitution or a point mutation)B. Frameshifts by insertion/deletion of a 1-2 basesC. Insertions and deletions of larger DNA fragments1. Gain or loss of 100-1000’s (or more) of bases2. Results in complete loss of gene function3. Some deletions might wipe out entire gene cluster4. Translocation:5. Inversion:6. Why/how does this happen?7. Big deletions in most cases are not revertible.D. Caused by deliberate insertion of DNA segments like:E. Back mutations or reversions1. Point mutations are usually reversible2. Restoration occurs by a counteractive mutation3. It is common that mutations that alter cellular metabolism have sufficient selective pressure for compensatory mutations that repair the original defect4. How back mutations arise:5. Types of suppressors:III. Rates of mutationA. Rate of mutation depends on the kinds of mutations1. some are rare others are frequent2. Some genes have “hot spots” for mutations.B. Do mutations arise by an adaptive response to a selective agent (acquired immunity) or are mutations spontaneously and continuously occurring in a culture and it is the selective process that reveals the specific mutation? (See slide for example)1. Fluctuation Test by Luria and Delbruck demonstrated that:IV. Chemical MutagensA. Spontaneous mutations vs. chemical mutagens:1. Some chemicals can significantly increase the natural rates of mutations2. Some chemicals exhibit specificity for a particular type of mutationB. Structural analogs of nucleotides (Fig. 13.32)1. 5-Bromouracil (BU)C. Agents that modify DNAD. DNA intercalating agents1. Acridine organe and ethidium bromideV. How to test if a chemical is mutagenic? You can use the Ames TestA. A bacterial test that measures how mutagenic a compound is (Box 13.2)B. Use the Ames Test as an indicator for a carcinogenic potential.Mutations in bacteria Bio119I. Mutations: what are they?A. They are changes in the DNA sequenceB. Can arise:C. Consequences of mutations in a haploid genome: D. If mutation is not repaired before next round of replication:E. Revision to wild-type is possible depending on the nature of the mutationII. Types of Mutations:A. Single base pair mutations (called a substitution or a point mutation)Page 1Mutations in bacteria Bio119B. Frameshifts by insertion/deletion of a 1-2 bases Page 2Mutations in bacteria Bio119C. Insertions and deletions of larger DNA fragments1. Gain or loss of 100-1000’s (or more) of bases2. Results in complete loss of gene function3. Some deletions might wipe out entire gene cluster4. Translocation: 5. Inversion:Page 3Mutations in bacteria Bio1196. Why/how does this happen? 7. Big deletions in most cases are not revertible.D. Caused by deliberate insertion of DNA segments like: E. Back mutations or reversions1. Point mutations are usually reversible2. Restoration occurs by a counteractive mutation3. It is common that mutations that alter cellular metabolism have sufficient selective pressure for compensatory mutations that repair the original defect4. How back mutations arise:5. Types of suppressors:Page 4Mutations in bacteria Bio119III. Rates of mutationA. Rate of mutation depends on the kinds of mutations1. some are rare others are frequent2. Some genes have “hot spots” for mutations.B. Do mutations arise by an adaptive response to a selective agent (acquired immunity) or are mutations spontaneously and continuouslyoccurring in a culture and it is the selective process that reveals the specific mutation? (See slide for example)1. Fluctuation Test by Luria and Delbruck demonstrated that:Page 5Mutations in bacteria Bio119IV.Chemical MutagensA. Spontaneous mutations vs. chemical mutagens:1. Some chemicals can significantly increase the natural rates of mutations2. Some chemicals exhibit specificity for a particular type of mutationB. Structural analogs of nucleotides (Fig. 13.32)1. 5-Bromouracil (BU) C. Agents that modify DNA Page 6Mutations in bacteria Bio119D. DNA intercalating agents1. Acridine organe and ethidium bromide V. How to test if a chemical is mutagenic? You can use the Ames TestA. A bacterial test that measures how mutagenic a compound is (Box 13.2)B. Use the Ames Test as an indicator for a carcinogenic potential.Page 7Mutations in bacteria Bio119Page


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