07 Genetic Recombination in Bacteria and Viruses

07 Genetic Recombination in Bacteria and Viruses - Sex and...

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Ménage a trois? Deadly sex Sex and recombination in bacteria conjugation transduction
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Bacterial infections were a major cause of death before the discovery of antibiotics Sir Alexander Fleming discovered penicillin in 1928 and eventually won the Nobel Prize Prior to this discovery, bacterial infections and plagues were major public health problems Antibiotics are overused and used improperly leading to development of antibiotic resistant bacteria…… Doktor Schnabel von Rom
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Why would anyone be interested in studying sex in bacteria? KILLER BUGS Antibiotic resistant strains of bacteria will likely be a major health problem in the future – how is antibiotic resistance spread? Necrotizing fasciitis / flesh-eating bacteria Black Death / the Bubonic Plague
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Genetic “exchange”in bacteria 1. Conjugation : transfer of plasmids, transfer of genome when plasmid is integrated. 1. Transduction : bacteriophage can “pick up” fragment of genome and deliver it to another cell. 1. Transformation : uptake of DNA fragments from extracellular environment All are essentially one- way transfers from donor to recipient
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Recombination lingo Donor: contributes a small piece of DNA, exogenote Recipient: receives DNA (has complete genome), endogenote Merozygote : contains endogenote and exogenote, a partial diploid, opportunity for recombination
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Bacteria are often easy to culture Can be rapidly grown in large quantities Cells divide by binary fission Growth medium can be liquid or solid, such as nutrient agar Colony: asexual descendents of single cell
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Prototrophs and auxotrophs Prototroph : wild-type bacterium that produces colonies on minimal medium Auxotroph : mutant that requires one or more nutrients in addition to minimal medium Usually designated by 2-3 letters with + or – symbol Examples of prototrophy / auxotrophy met + : can synthesize methionine, a wild-type prototroph met : requires methionine, a mutant auxotroph
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Energy utilization and drug resistance Energy extraction gal + : can utilize galactose, wild-type gal : lost the ability to utilize galactose, a mutant Drug resistance: often due to a plasmid DNA str r : resistant to streptomycin in medium str s : sensitive to streptomycin in medium Antibiotic resistance is very useful in the molecular biology lab, but it’s an emerging problem in medicine
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Selective systems to isolate the mutant Allows the desired mutant to reproduce antibiotic resistance minimal medium supplemented with specific nutrient Revertant: reverse change from mutant to wild-type similar selection regimens
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William Vitek, Associate Professor of Philosophy Clarkson University Department of Biology Seminar Friday, February 3 at 2 PM Room 212 Bertrand Snell Hall Apes in Lab Coats: Urging Precaution in the Church of Science
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Why is everyone so worried about bird flu?
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07 Genetic Recombination in Bacteria and Viruses - Sex and...

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