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Chapter 9 - Chapter 9 Gene Transfer Mutations and Genome...

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Chapter 9 Gene Transfer, Mutations, and Genome Evolution DNA sequence is not static (Do not stay the same, they can change) Horizontal gene transfer (from one organism to another) Transformation Conjugation Transduction Mutations (also could change DNA sequences besides HGT) Deletions (see above) Insertions (see above) Effects of Gene Transfer Spreads useful genes among bacteria Antibiotic-resistance genes Spread wherever antibiotics are overused Hospitals, farms Pathogenicity islands Encode genes for cell to act as pathogen Difference between typical E. coli in gut and pathogenic E. coli 0157H7 (this 0157H7 has a pathogenicity island, came from shigella species) Genes to degrade special metabolites (oil spills clean up) Mechanisms of horizontal gene transfer Transformation Transduction Conjugation
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Transformation- competent (cell with the ability) cell picks up free DNA from the environment. When this cell dies it gets chopped up into little pieces and other bacs pick up the free DNA it had. Some cells are naturally competent ( Bacillus ) Some cells can be made competent: Salt treatments Electroporation - electrical shock opens pores in cell membrane, DNA enters through pores. (pore must be open very briefly. Kills a lot of the cells, but has a pretty high success rate) If free DNA isn’t incorporated into chromosome, it will be degraded . Free DNA can’t replicate on its own. Transduction – bacterial DNA is transferred from one bacterium to another by a virus. Bacteriophage injects DNA into host DNA is packaged into viral capsid Normally viral DNA is packaged Rarely, baterial DNA is packaged by mistake DNA is transferred to new host Can bring new bacterial genes to host Generalized transduction - During viral infection, random pieces of bacterial DNA are accidentally packaged into viral capsid. Any part of the host chromosome can be transferred to a recipient cell.
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