Chapter 8-How Transcriptional switches work

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  1. _______ switches allows cells to respond to changes in the environment.

    a ____________ __________ interacts with the major groove of a DNA double helix and form tight associations with the base pairs in a short stretch of DNA to act as the switch to control transcription. 

    Proteins that recognize a specific nucleotide sequence do so because?

    Many transcription regulators bind to the DNA helix as ______.

    transcription regulator

    The surface of the protein fits tightly against the surface features of the DNA double helix in that region.

  2. Clusters on a chromosome transcribed from a single promotor as one long mRNA producing Tryptophan.

    When trp concentration is low, the operon is _______.

    What happens when the regulator is bound to the operator?

    The transcription regulator is known as the?

    What is required for the repressor when it binds to the DNA?


    It blocks access of RNA polymerase to the promotor, preventing transcription of the operon and production of the tryptophan-producing enzyme.

    Tryptophan repressor.

    Several bound trp.
  3. What happens when the conc. of trp is too low?

    Due to this, what does it mean for the repressor?
    The repressor no longer binds to DNA and the tryptophan operon is transcribed.

    It is a molecular switch that works according to the availability of the end product of the pathway that the enzymes catalyze, when too much, the repressor binds to the operon, when too low, it doesn't and operon is transcribed.
  4. An _____ ______ binds to a regulatory sequence on the DNA and then interacts with the RNA polymerase to help it initiate transcription.

    The activator proteins often have to interact with a ________ molecule to be able to bind

    An example of the activator protein would be the CAP protein associated with cyclic AMP before it can bind to ____?

  5. What control the Lac Operon?

    The Lac operon encode proteins required to do what? or it produces proteins to do what?

    What controls the Lac operon?
    An Activator and a Repressor.

    Import and digest the disaccharide Lactose.

    Lac repressor and the CAP activator.
  6. In the absence of glucose, the cell makes cAMP that binds with the ________ which activates it
    to switch on genes that allow the cell to utilize alternative sources of carbon-including _______.

    For the operon to be on, what must be present?


    Absence of glucose, produces cAMP which binds to CAP and when Lactose is present, the operon turns on and used for a source of energy.
  7. Eukaryotic _______ ________ control gene expression from a distance away from the promoter.
    What are enhancers?
    Why are they called enhancers?
    They also work when located.....
    Transcription regulators.

    • DNA sites in which eukaryotic transcription regulators bind to.
    • Because they enhance the rate of transcription.
    • Upstream or downstream from the gene.
  8. What does the eukaryotic activator protein that is bound to a distant enhancer attract to the promoter?

    What does the looping do?

    What is the mediator?

    What is the TATA box?
    RNA polymerase, mediator, and general transcription factors to start transcription.

    Permits the contact between the activator protein and mediator (transcription initiation complex).

    It is a large protein complex that attracts large transcription factors and RNA polymerase to form the large transcription complex at the promotor, also serves to link the activator protein as the enhancer.

    It is a DNA recognition sequence for the first general transcription factor that binds to the promoter.
  9. Process of gene activation that occur at a distance.

    Where is the first general transcription factor bound to?
    • 1. Euk. activator protein bound to the enhancer.
    • 2. Activator protein attract general transcription factors, mediator, and RNA polymerase.
    • 3. Looping allows the connection of the activator protein with the mediator.
    • 4. All located right before the TATA box which is a DNA recognition sequence for the first general transcription factor that binds to the promoter.

    The promotor, upstream from the TATA box.
  10. Eukaryotic Transcription regulators help initiate transcription by recruiting ________-_________ proteins.

    Do nucleosome inhibit the initiation of transcription if they are positioned over a promoter because they physically block the assembly of the general transcription factors or RNA polymerase on the promoter.

  11. Activator and repressor proteins exploit chromatin structure to help turn genes on and off.

    Chromatin structure can be altered by two things. What are they?

    What is the enzyme used that covalently modifies the histone proteins that form the core of the nucleosome. How? What do the acetyl groups do?
    • 1. Chromatin-remodeling complex.
    • 2. Enzymes that covalently modify the his ton proteins that form the core of the nucleosome.

    • Acetyl transferase.
    • It promotes the attachment of acetyl groups to selected lysines in the tail of histone proteins, allowing greater accessibility to the underlying DNA.
    • They attract proteins that promote transcription, general transcription factors.
  12. Eukaryotic Transcription regulators can...
    • 1 Recruit chromatin-modifying proteins to help initiate gene transcription such as acetyl transferase and chromatin-remodeling complex.
    • 2. Control gene expression from a distance using activator protein and enhancer with mediator.
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Chapter 8-How Transcriptional switches work
2014-10-30 06:44:04
chapter 8
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