Bmsc210 M2 p4

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Bmsc210 M2 p4
2013-03-08 17:28:43
Bmsc210 M2 p4

Bmsc210 M2 p4
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  1. Recombination
    • – Physical exchange of DNA between genetic elements
    • -Selective medium can be used to detect raregenetic recombinants
  2. Homologous recombination
    – Process that results in genetic exchange between homologous DNA from two different sources (Figure 10.10
  3. Transformation
    • – Genetic transfer process by which DNA is incorporated into a recipient cell and brings about genetic change
    • - Discovered by Fredrick Griffith in the late 1920s
    • – Worked with Streptococcus pneumoniae (pneumococcus; Figure 10.12)
    • 􀅖 This process set the stage for the discovery of DNA
  4. Cell Competence:
    • -ability of cells to take up DNA and be transformed
    • – In naturally transformable bacteria, competence is regulated
    • – In other strains, specific procedures are necessary to make cells competent
    • – Electricity can be used to force cells to take up DNA (electroporation)
  5. electroporation
    When Electricity is used to force cells to take up DNA
  6. During natural transformation, integration of transforming DNA is a highly _____ , multistep process
  7. Transduction
    2 modes
    • – Transfer of DNA from one cell to another by abacteriophage
    • – Two modes:
    • • Generalized transduction
    • • Specialized transduction
  8. Generalized transduction:
    (3 characteristics)
    • DNA derived fromvirtually any portion of the host genome ispackaged inside the mature virion
    • – Defective virus particle incorporates fragment ofthe cell’s chromosome randomly– Virus can be temperate or virulent
    • – Low efficiency
  9. Specialized transduction:
    DNA from a specific region of the host chromosome is integrated directly into the virus genome
  10. Bacterial conjugation (mating):
    mechanism of genetic transfer that involves cell-to-cell contact– Plasmid-encoded mechanism
  11. Bacterial conjugation (mating)
    Donor cell:
    Recipient cell:
    • -Donor contains conjugative plasmid
    • - recipient does not contain plasmid
  12. F (fertility) plasmid (Figure 10.16)
    (4 points)
    • – Circular DNA molecule; ~100 kbp– Contains genes that regulate DNA replication– Contains several transposable elements that allow the plasmid to integrate into the hostchromosome
    • – Contains tra genes that encode transfer functions
  13. F plasmid is an ______; can integrate into host chromosome
  14. Cells possessing a nonintegrated F plasmidare called ___
  15. Cells possessing an integrated F plasmid are called __
    •  Hfr (high frequency of recombination)
    • – High rates of genetic recombination between genes on the donor chromosome and those of the recipient
  16. Does the recipient cell become Hfr?
    Recipient cell does not become Hfr because only a portion of the integrated F plasmid is transferred by the donor
  17. What conditions do the Identification of recombinant strains require
    Identification of recombinant strains requires selective conditions in which the desired recombinants can grow but where neither of the parental strains can grow
  18. What can Genetic crosses with Hfr strains be used for?
    Genetic crosses with Hfr strains can be used to map the order of genes on the chromosome (Figure 10.24)