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Gene Expression in Bacteria

  1. Which point of gene expression will cause the most rapid change in a protein that controls a particular trait?



    B) post-translational modification
  2. Gene Expression
    • Process of converting information stored in DNA into active gene product (protein)
    • Both prokaryotes and eukaryotes precisely regulate their gene expression
    • Can be controlled in multiple steps 
    • -Gene is not just ON or OFF (levels of expression can vary)
  3. Bacterial gene regulation
    • Bacteria can often on/off pathways in response to changing environmental conditions
    • Example- E. coli living in a human colon needs tryptophan to survive, so if a person doesn't have it then it needs to make it. But, why should bacteria make it if the human has it
  4. Operons
    Cluster of co-transcribed genes with related functions
  5. 3 basic components of operons
    • Promoter
    • Operator
    • Structural genes
  6. Promoter
    Where RNA polymerase can bind and begin transcription
  7. Operator
    Segment of DNA that acts as the on/off switch, where repressor binds (can be within promoter or between promoter and genes)
  8. Structural genes
    The genes that are co-regulated
  9. For a responsible operon to be transcribed, which of the following must occur?



    B) RNA polymerase must bind to the promoter, and the repressor must be inactive
  10. A mutation that inactivates the regulatory gene of a repressible operon in an E. Coli cell would result in...
    Continuous transcription of the structural genes controlled by that regulator
  11. Lac operon
    • Contains genes which code for enzymes necessary to transport and metabolize lactose
    • Inducible
    • Repressor (coded for by lacl) is active by itself
    • -an inducer is needed to bind to it and inactivate it 
    • -Allocatose (an isomer of lactose) is the inducer
  12. Inducible
    Usually turned off but can be switched on
  13. Transcription of the structural genes in an inducible operon...
    Starts when the pathway's substrate is present
  14. Suppose an experimenter becomes proficient with a technique that allows her to move DNA sequences within a prokaryotic genome. If she moves the promoter for the lac operon to the region between the beta galactosidase (lacz) gene & the permease (lacy), which of the following would be likely?



    A) Beta galactosidase will not be produced
  15. Suppose an experimenter becomes proficient with a technique that allows her to move DNA sequences within a prokaryotic genome. If she moves the operator to the far end of the operon, past the transacetylace (lac A) gene, which of the following would likely occur when the cell is exposed to lactose?




    C) the structural gene will be transcribed continuously
  16. Positive regulation of the lac operon
    • Glucose is preferred energy for E. coli
    • Only uses lactose if glucose is in low supply
  17. How does the bacteria know when to use the lac operon?
    • cAMP accumulates when glucose is scarse
    • cAMP activates CAP (catabolite activator protein) which binds to lac promoter and increases the affinity of RNA polymerase for the promoter)
    • -- When glucose is low it accumulates cAMP which is what activates CAP
  18. Trp operon
    • Contains the genes which code for the enzymes needed to synthesize tryptophan
    • Repressible
    • --The bacteria always needs tryptophan so it it's present they don't need to make more
    • Trp repressor can bind to operator and block polymerase= shuts it off
    • -Trp repressor is inactive unless tryptophan (a corepressor) binds to it
  19. Repressible
    Usually turned on but can be inhibited
  20. What if bacteria need to coordinate a large number of genes?
    • Alternative sigma proteins
    • Regulons
  21. Regulon
    • Set of separate genes (or operons) controlled by a single regulatory protein
    • -- one thing would turn on multiple operons
  22. Which of the following statements about the DNA in one of your brain cells is true?




    C) It is the same as the DNA in one of your heart cells
Author
Zaqxz
ID
336696
Card Set
Gene Expression in Bacteria
Description
alkdf
Updated

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