3.1.1

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Author:
efrain12
ID:
206071
Filename:
3.1.1
Updated:
2013-03-11 00:54:50
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bios
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gene expression in prokaryotes
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  1. Which of the following are used to regulate gene expression and function? (3)
    -transcriptional control

    -translational control

    -Post-translational modification
  2. What best defines the term operon?
    -an operon is a region of DNA that codes for series of functionality related genes under the control of the same promoter
  3. Under which conditions are the lac structural genes expressed most efficiently? (2)
    - no glucose and high lactose
  4. In what 3 levels can gene expression be controlled at?
    -transcription

    -translation

    • -post-translation 
    • *protein activation
  5. What is the lac operon?
    a model system for understanding fundamental mechanisms regulating gene expression
  6. What two types of transcriptional control can a regulatory protein induce?
    negative and positive
  7. (transcriptional control) Negative control
    prevent transcription
  8. (transcriptional control) Positive control
    increases the transcription rate
  9. Regulatory proteins AND distinct amino acid sequence AND type binds to different DNA sequences
    Each type of regulatory protein has a distinct amino acid sequence therefore each binds to different DNA sequences
  10. (regulation of gene expressions ) Transcriptional control (2)
    - we can regulate to determine whether or not we will let RNA polymerase to produce a transcript

    -it is slow but efficient with the energy expenditure
  11. (regulation of gene expressions ) Transcriptional control (2)
    -whether or not we will end up producing the protein from the ribosome

    • -allows quick change to which proteins are produced
    • *expends little energy
  12. (regulation of gene expressions ) Post translational control (3)
    • -we can produce the protein then decide if it will have a potent function by modifying it
    • *putting a phosphate

    -very rapid response

    -energetically expensive
  13. WHat two conditions does E.coli make machinery to process lactose? (2)
    -no glucose around

    -lots of lactose around
  14. What is the galactoside permease?
    protein that gives a channel to cross over the hydrophobic membrane
  15. What is the Beta galactoside?
    • enzyme that breaks up lactose up into single units
    • *glucose and galactose
  16. What are the two proteins that process the lactose?
    -Galactoside permease

    -Beta-galactoside
  17. What is lactose broken into? (2)
    glucose and galactose
  18. Mutant Phenotype: Cells cannot cleave indicator molecule even if lactose is present as an inducer

    Interpretation? (2)
    -No beta-glucosidase

    -gene for beta glucosidase is defective
  19. Mutant Phenotype: Cells cannot accumulate lactose inside the cell

    Interpretation? (2)
    -No membrane protein required for import of lactose

    -gene for galactoside permease is defective
  20. Mutant Phenotype: Indicator is cleaved even if lactose is absent (no inducer)

    Interpretation? (3)
    -constitutive expression of lacZ and lacY

    -gene for regulatory protein that shuts down lacZ and lacY is defective

    -it does not need to be induced by lactose
  21. What does lacZ + stand for?
    does produce beta galactosidase
  22. What does LacZ- stand for?
    does not produce beta galactosidase
  23. What does lacY+ stand for?
    produces galactoside permease
  24. What does LacY- stand for?
    does not produce galactoside permease
  25. LacI-?
    produces the 2 proteins without lactose inducing the repressor
  26. Does E.Coli continuously produce the 2 proteins?
    no, because making these proteins expends alot of energy
  27. What is a polycistronic system?
    • expression of many genes are turned up or down by a single regulatory factor
    • *lacI
  28. Which is the regulator in the lac operon?
    lacI
  29. (Regulation of the lac operon diagram) diagram A (4)
    -repressor present

    -lactose absent

    -repressor binds to DNA

    -no transcription occurs
  30. (Regulation of the lac operon diagram) diagram B (4)

    -repressor present

    -lactose present

    • -lactose binds to repressor causing to release from DNA
    • *acts as inducer

    -transcription occurs
  31. (Regulation of the lac operon diagram) diagram C (3)

    -no repressor present

    -lactose present or absent

    -transcription occurs
  32. What is the inducer of this system>
    lactose induces this change
  33. What is a domain?
    a distinctive 3 dimensional structure and function that proteins have
  34. What is a motif?
    domain that is observed in many different proteins
  35. What is a common structural design in the lac repressor?
    helix-turn-helix motif
  36. What does helix turn helix do?
    the motif fits easily into the major groove of the DNA double helix
  37. What binds to operator region?
    repressor protein
  38. What binds to the promoter regions ?
    sigma protein
  39. What is negative control? (2)
    -regulatory protein shuts down transcription

    -repressor protein is normally present preventing transcription which saves energy
  40. In the system when we have lactose inducing the prodcution of genes, is that negative control?
    yes
  41. What is positive control?
    regulatory protein triggers transcription
  42. Regulation of the gene products of the lac Z and LacY by LacI is an example of?
    negative control
  43. (regulation of the lac operon by glucose) Catabolite repression
    when glucose levels are high, trasncription is turned off even if lactose levels are high

    *example of feedback inhibition
  44. (regulation of the lac operon by glucose) Catabolism formula
    -large reactant molecule >(enzyme)> small product molecule + small product molecule (catabolites

    ex) Lactose >Beta galactosidase> galactose + glucose
  45. (regulation of the lac operon by glucose) Catabolism
    break down of a large product into small ones
  46. (regulation of the lac operon by glucose)(catabolite repression) How does glucose inhibit hte catabolite repression?
    glucose does not directly bind to DNA or RNA to inhibit process, it alters the concentration of other molecules
  47. (regulation of the lac operon by glucose)(catabolite repression) WHat triggers transcription?
    the CAP binds to the CAP binding site near the lac promoter 

    *positive control
  48. (regulation of the lac operon by glucose)(catabolite repression) What are the effects of the CAP binding?
    lac promoter increases expression
  49. (regulation of the lac operon by glucose)(catabolite repression) How is CAP regulated?
    by cyclic AMP (cAMP) binding to it
  50. (regulation of the lac operon by glucose)(catabolite repression) what needs to happen in order for the CAP to bind well with the DNA?
    CAP needs to be binded with cAMP
  51. (regulation of the lac operon by glucose)(catabolite repression) What happens if cAMP levels are low?
    CAP is not active and transcription is not increased
  52. (regulation of the lac operon by glucose)(catabolite repression) What happens when cAMP levels are high?
    CAP protein binds to DNA and speeds up trasncription
  53. (regulation of the lac operon by glucose)(catabolite repression) What does glucose lower the concentration of?
    cAMP by altering the activity of the adenylate cyclase (makes cAMP)
  54. (regulation of the lac operon by glucose)(catabolite repression)What happens if there is a large number of glucose present?
    leads to a drop on cAMP
  55. If cAMP are high, will we get an increase in beta glucosidase and mRNA?
    yes
  56. Do we get an increase in beta glucosidase when glucose levels are high?
    no, we dont need to produce enzymes and proteins needed for lactose

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