Describe - Gene Transfer


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binary fisson, conjugation, transposons, transduction, transformation, plasmids, insertion sequences, dissemination of drug resistance in bacteria, genetic transfer in bacteria, theta replication, rolling circle replication

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Describe - Gene Transfer

  1. 1. Describe: gene transfer b.stev
  2. 2. <ul><li>METHODS - gene transfer between bacteria: </li></ul><ul><li>binary fission </li></ul><ul><li>conjugation </li></ul><ul><li>transformation </li></ul><ul><li>transduction </li></ul><ul><li>transposons </li></ul>
  3. 3. <ul><li>REPLICATES before cell division: </li></ul><ul><li>two daughter cells attached > interior of cell membrane </li></ul><ul><li>membrane elongates, chromosomes move apart </li></ul><ul><li>cell doubles in size: chromosomes separate </li></ul><ul><li>the cell THEN “ pinches” inwards... </li></ul><ul><li>a new cell wall forms that separates the two new </li></ul><ul><li>cells and their chromosomal replicas </li></ul>ALL genetic material contained is transferred to the daughter cell (Barnes S. N, Curtis H, 1989) Binary fission
  4. 4. cell wall chromosome cell membrane theta replication growth of cell NEXT REPLICATION
  5. 5. new cell wall forms REPLICATED bacterial cells (two identical daughter cells)
  6. 6. This type of replication is known as: THETA REPLICATION a bi-directional motion DNA helix unwinds/ replicates / rewinds
  7. 7. cell F- cell F+ bacterial chromosome F plasmid bacteria join: pili transfer of F plasmid cell F+ transfer provides: COMPLEMENTARY DNA CONJUGATION
  8. 8. PLASMIDS <ul><li>are small pockets of DNA that occur in bacteria </li></ul><ul><li>carry genetic material for a specific purpose </li></ul><ul><li>plasmids often conjugate to another bacterium </li></ul><ul><li>THIS: </li></ul><ul><li>provides the bacterium with complementary DNA </li></ul><ul><li>KNOWN AS,” rolling circle replication ” </li></ul>plasmid moves to bacterium via the use of an extension made by host [ carrier ] cell: - this extension is called: pili (Barnes S. N, Curtis H, 1989)
  9. 9. <ul><li>DNA fragment is absorbed through the cell membrane and utilised in function (expressed) </li></ul><ul><li>enhanced drug resistance from the acquisition </li></ul><ul><li>of plasmids OR/& DNA fragment(s) </li></ul><ul><li>occurs in crowded environments like a rich soil </li></ul><ul><li>OR within the human intestinal tract </li></ul>Transformation NOTE: not significant in contribution to the dispersal of antibiotic resistant genes
  10. 10. Transduction
  11. 11. SPECIALISED> prophage – the altered bacterial DNA performs BINARY FISSION that creates replicates though the replicates differ: ONE may produce virus cells OTHER creates defective virus cells that seek to perform the process of: generalised transduction (Pommerville J.C, 2004)
  12. 12. Insertion Sequences small segments DNA: about 1000bp <ul><li>INSERTION OCCURS AT: </li></ul><ul><li>one/ more sites on bacterial chromosome/ plasmids </li></ul><ul><li>no genetic information other than ability to insert </li></ul><ul><li>form copies of themselves & these move to other </li></ul><ul><li>areas of the chromosome </li></ul><ul><li>can interrupt a coding sequence of protein(s) </li></ul><ul><li>may be some cause behind: spontaneous mutation </li></ul><ul><li>induces wrong protein(s)/ no protein(s) forms </li></ul>
  13. 13. <ul><li>interrupts genetic code of the gene </li></ul><ul><li>appears NOT be replaced once,’disembarked’ </li></ul><ul><li>can move from: plasmid/plasmid </li></ul><ul><li>plasmid/chromosome </li></ul><ul><li>chromosome/plasmid </li></ul><ul><li>thought to serve as evolutionary driving force: </li></ul><ul><li>development, fertilized egg to mature organism </li></ul>Transposons larger insertion sequences that have the ability: carry information such as antibiotic resistance
  14. 14. C C C T A A T T A G G G G G G A T T A A T C C C inverted sequence of repetitive bases: ability to move/ insert & disembark coded sequence of information TRANSPOSON
  15. 15. Genetic Transfer & dissemination of drug resistance Transfer, causes increase in bacterial population that have the ability to resist specific drugs: <ul><li>Evolved to alter their manufacture of the </li></ul><ul><li>required protein(s), so the drug pathway: </li></ul><ul><li>has altered chemical attachment points </li></ul><ul><li>enzymes can counteract chemical bonding </li></ul><ul><li>other metabolic means are able to be used </li></ul>
  16. 16. OVERUSE & MISUSE ENCOURAGES RESISTANT FORMS: 1968-71 > Guatemala ; 12,000 people died to a resistant form of: S.dysenteriae ANTIBIOTICS causes the sensitive cells to die, stimulates resistant cells: grow & to thrive increasing numbers HOSPITALS: care taken to prevent resistant strains overtaking the susceptible strains especially: E.Coli P.Aeruginosa S.Marcesens Proteus (Pommerville J.C, 2004)
  17. 17. <ul><li>PLASMIDS and TRANSPOSONS cause the most movement of the antibiotic resistant genes </li></ul><ul><li>resistance can occur in harmless bacteria </li></ul><ul><li>that transfer this to pathogenic bacteria: </li></ul><ul><li>ALSO increasing potential of disease </li></ul><ul><li>LIVESTOCK fed with antibiotics is traceable </li></ul><ul><li>to human consumption; and thus may also </li></ul><ul><li>through the cycle of bacterial growth: gain </li></ul><ul><li>resistance over the time of exposure to the </li></ul><ul><li>drug: ALSO increasing potential of disease </li></ul>
  18. 18. Bibliography Campbell N. A, Reece J. B. (2005). Biology (7th ed.) . San Francisco: Benjamin Cummings Pommerville J.C. (2004). Alcamo’s – Fundamentals of Microbiology (7 th ed.). Massachusetts: Jones and Bartlett. Barnes S. N, Curtis H. (1989). Biology (5th ed.) . New York: Worth