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Announcements

Announcements. Seminar today at noon Lab notebooks are due today by 5 PM Ch. 8 Part 2 Homework due Wednesday Review Session for Test 2? Monday March 3 rd Tuesday March 4 th. Bacterial Genetics Ch. 8 Part 2. Question (2 Mins ). What is one way to induce genetic change in bacteria?

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Announcements

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  1. Announcements • Seminar today at noon • Lab notebooks are due today by 5 PM • Ch. 8 Part 2 Homework due Wednesday • Review Session for Test 2? • Monday March 3rd • Tuesday March4th

  2. Bacterial Genetics Ch. 8 Part 2

  3. Question (2 Mins) What is one way to induce genetic change in bacteria? Answer: Mutations

  4. Horizontal Gene Transfer • Another method for genetic change in bacteria • The acquisition of genes from other cells • 3 mechanisms • DNA-mediated transformation • Transduction • Conjugation

  5. How does newly acquired DNA get passed onto daughter cells?

  6. DNA Must Have An Ori Or Undergo Homologous Recombination To Pass DNA To Daughter Cells • What DNA have an ori (origin of replication)? • Plasmids • Chromosomes • Parts of chromosomes do not • If no ori, must be incorporated into DNA via homologous recombination

  7. Homologous Recombination

  8. Horizontal Gene Transfer: DNA-Mediated Transformation • When bacteria take up naked DNA • What is naked DNA? • DNA free in the cell’s surrounding • Not contained in a cell or virus • How do you know it’s naked? • Add DNase=no transformation • Where does the DNA come from? • Other cells secrete it or when cells die they release it

  9. Can All Bacteria Take Up Naked DNA? • No, the cells must be competent • A physiological state that allows DNA uptake • What allows a cell to become competent? • Some cells are always naturally competent • Some cells sense their surroundings, respond by turning on genes necessary for competence

  10. T R A N S F O R M A T I O N

  11. Horizontal Gene Transfer: Transduction • Bacterial viruses aka bacteriophages/phage transfer bacterial genes from a donor to recipient

  12. First, Let’s Talk Phage • Phage is a virus that infects bacteria • Phage contains genetic material of DNA OR RNA (never both) • Genetic material is surrounded by a protein coat • Phage attaches to a cell and injects its genetic material

  13. Horizontal Gene Transfer: Transduction

  14. Horizontal Gene Transfer: Conjugation • Conjugation = “con”tact between donor and recipient cells • What is transferred? • Plasmids • Do they have ori? Yes • Most studied and understood: F plasmid (fertility) • Cell harboring the F plasmid: F+ • Cell without the F plasmid: F- • How the plasmid is transferred: F pilus (sex pilus)

  15. Horizontal Gene Transfer: Conjugation

  16. Activity (15 mins) • Your paper bag is a bacterium, we are Streptococcus pyogenes(strep throat) in a • Discs in your bag represent a plasmid • White: Plasmids without a gene for antibiotic resistance • Purple: Plasmids with a gene for penicillin resistance • Record here___________ the color of your discs • Go to another student and exchange a disk with another student’s bacterium: DO NOT LOOK IN BAG WHEN EXCHANGING • Repeat the exchange 4 additional times (for a total of 5) • No record the number and color of your discs here_________________________________

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