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Bacterial Genetics

Bacterial Genetics. Asexually reproducing (binary fission) High reproductive rates/short generation spans Variation in bacteria mainly caused by mutation Our variation mainly caused by recombination of existing alleles. Sources:.

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Bacterial Genetics

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  1. Bacterial Genetics • Asexually reproducing (binary fission) • High reproductive rates/short generation spans • Variation in bacteria mainly caused by mutation • Our variation mainly caused by recombination of existing alleles

  2. Sources: Although there is no meiosis, recombination of alleles can occur • Transformation (we will do a lab after exams) • Transduction • Conjugation

  3. Transduction • Viruses may transfer (act as vector) DNA from one bacteria to another • New bacterial DNA may line up with a homologous section of the bacterial chromosome and recombination (crossing over) may occur • May be GENERALIZED TRANSDUCTION or SPECIALIZED TRANSDUCTION

  4. Generalized transduction • Virus is in the lytic cycle • Bacterial DNA that was degraded accidentally is incorporated into viral capsid • Capsid injects bacterial DNA into new bacteria • The genes transferred are random

  5. Specialized transduction • Occurs from temperate viruses (in lysogenic cycle) • Prophage comes out of bacterial chromosome and take adjacent genes with it • Only specific genes are transferred in this way

  6. Conjugation • Bacterial “Sex” • Many bacteria have plasmids • Small circular pieces of DNA separate from chromosome • Contain only a few genes • Not necessary to bacteria’s survival • May give an advantage under certain environmental conditions

  7. F plasmids • Have genes that allow bacteria to form sex pilli

  8. F plasmid • Plasmids are transferred through the sex pilus during conjugation • A copy of plasmid is first made then transferred • F+ transfers to F-

  9. R plasmid • Plasmid containing genes that make bacterial RESISTANT to antibiotics • May have up to 10 antibiotic resistance genes on one plasmid • Made possible by TRANSPOSONS

  10. Transformation • Gets its name from Griffiths experiment with mice • When bacteria take up foreign DNA from their surroundings • Some bacteria do this naturally • Some can be induced to do this (made “competent” • Important in E. coli to take up plasmids that have been created to carry certain genes

  11. Anatomy of the lac operon

  12. The operator determines whether transcription will occur by being able to bind with a regulatory protein

  13. The regulatory gene codes for the regulatory protein which is a repressor molecule

  14. Active repressor prevents transcription

  15. Effect of lactose on the lac operon

  16. Energy preference of E.coli

  17. The concentration of glucose is inversely proportional to the concentration of cyclic AMP Cyclic AMP binds with an activator protein and helps RNA polymerase to bind to the promoter

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