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UT Knoxville BIOL 240 - Bacterial Genetics

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BIOL 240 1st Edition Lecture 15Outline of Last Lecture I. InversionsII. Gene Duplication and Genome EvolutionIII. Alternative fates of duplicated genesIV. GlobinsOutline of Current Lecture I. Bacterial GenomeII. Genotypic SymbolsIII. Bacterial DNA ExchangeCurrent LectureI. Bacterial Genome- Single, circular chromosome called plasmid- Plasmids carry genes that are not essential but may benefit the cell (such as resistance or fertility), so they may be present or absent.- E. coli—nucleoid is the genome; 6 million base pairs- Bacterial colonies can be plated—a suspension of bacterial cells is spread on agar in a petri dish and incubated. Soon, colonies appear, each is a clone of the corresponding single cell.II. Genotypic Symbols- Bio- means that the cell cannot produce biotin on its own and requires it added to the medium to grow- Arg- means that the cell cannot produce arginine on its own and requires it added to the medium to grow- Met- means that the cell cannot produce methionine on its own and requires it added to the medium to grow- Lac- means that the cell cannot use lactose as a carbon source- Gal- means that the cell cannot use galactose as a carbon source- Strr means the cell is resistant to the antibiotic streptomycin- Strs means the cell is susceptible to the antibiotic streptomycin- Prototrophic (wild-type)—can grow on minimal mediaThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- Auxotrophic (mutant)—require nutritional supplement to growIII. Bacterial DNA Exchange- Transformation—partial genome transfer by DNA uptake- Conjugation—plasmid transfer (requires cell to cell contact)o Major form of recombinationo Discovered by Lederburg and Tatumo Two different auxotrophic strains of bacterial were grown separately in complete medium. When plated separately on minimal medium, nogrowth occurred. After being mixed together and plated on minimal medium, colonies of prototrophs grew.o An F+ strain and an F- strain were put into a U-tube along with a filter. The medium was allowed to pass through the filter, but the cells were not. No growth occurs when plated. This is evidence that recombination requires cell to cell contact.o F plasmid is required; matings occur between F+ (donor) cells and F- (recipient) cells. A copy of the F plasmid from the donor cell is transferred to the recipient cell, resulting in both the donor and recipient being F+ cells at the end. The F plasmid is replicated by a rolling circle mechanism that produces a single copy of the F plasmid that is fed into the recipient cell through a pilus.- Transduction—transfer as part of viral


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