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48 Cards in this Set
- Front
- Back
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Constitutive
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Constant, unregulatated transcription
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Induction
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Increased transcription, positive regulation
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Repression
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Decrease transcription, negative regulation
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What is the difference between strong and weak promoters?
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Strong promoters match the consensus well, while the weak promoters diverge from consensus.
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Where does the promoter specificity reside in the RNA polymerase?
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Sigma subunit
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What do sigma 32 subunits recognize?
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Heat shock promoters which are turned on during excessive insult to the cell usually in the form of heat.
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Where do the consensus sequences reside in the sigma 70 promoters?
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-35 and -10 region
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Repressors
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Impeded access of RNA polymerase to the promoter
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Activators
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Enhance access of RNA polymerase to the promoter
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Operator
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Region of the DNA that binds to the repressor.
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What kind of mRNA message do operons generate?
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Polycistronic mRNA
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What are the functions of the lac operon genes?
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Encode genes required for use of lactose as a carbon source:
1) Primase - allows for entry 2) B-galactosidase - which cleaves the disaccharides |
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What is gene codes for the lac repressor? Where is it found?
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Lac I which is found upstream lac operon promoter.
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Where does the lac repressor bind?
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Primary lac operator as well as one of the two secondary lac operators.
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What happens in the presence of allolactose?
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Allolactose binds to repressor, preventing its binding to the DNA and inducing transcription
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How strong is the lac operon promoter? What does this mean for transcription.
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The promoter is suboptimal meaning activation is necessary for high levels of transcription.
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In the lac operon, how is activation achieved?
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CRP helps recruit RNA polymerase to the promoter.
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What is the function of the trp operon gene?
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Coding protein required for the biosynthesis of trp amino acid.
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In the trp operon, what is trp?
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Co-repressor
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Most importantly, in the transcription attenuation of the trp operon, what does the leader peptide contain?
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Tandem pair of trp
Region 2,3,4 |
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How does the leader pair sense trp levels?
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Translation of tandem pair of trp in the leader peptide requires charged tRNAs carrying the trp amino acid.
If trp is scarce, this pauses translation. |
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Which pairs in the leader sequence can base pair? What is the function of each pairing?
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2 and 3 or 3 and 4 (mutually exclusive)
3 and 4 generates a stem and loop structure that blocks translation. |
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What prevents the binding of region 2 and 3?
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When trp levels are high the ribosomes move quickly and cover up the region 2, preventing its paring with region 3 (which has not even been transcribed)
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Which operon regulates completely through attenuation?
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Histidine
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HAT
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Histone Acetly Transferase
Place acetly groups on histones, changing charge, opening up the chromatin and mark chromatin for further opening. |
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HDAC
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Histone Deacetylase; help close down chromatin
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What is the major way of regulation transcription in eurkaryotes? Why?
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Activation; Repression does not occur as much because:
1) Eukaryotic genome is too large to synthesize a different repressor for every gene. 2)Repressors are redundant to chromatin masking of promoters. |
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In eukaryotes, how do we ensure specificity in transcriptional regulation?
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Through multiple activators.
Required since the genome is so large and it's likely that one activator may bind incorrectly. |
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What are the three classes of proteins needed for transcriptional activation?
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Basal transcription factor
Transactivators Co-activators |
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Basal transcription factors
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These are unregulated and recurit RNAP to the promoter.
Rate of transcription is low. TBP and other TFII |
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Transactivators
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These are sensitive to regulation and bind to DNA at enhancers
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Co-activators
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These are non-DNA binding and their function is to mediate interactions between RNAP and transactivator.
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HMG protein
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facilitate looping
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Mediator
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Major co-activator in all eukaryotes which interacts with RNAP and transactivators.
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How does repression occur in eukaryotes?
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They are not bound to a specific operator sequence. Instead, they interfere with activity of mediator, transctivators and of RNAP and mediators.
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How are genes coordinately regulated in eukaryotes?
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By using the same activators for various genes.
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In yeast galactose metabolism, what is the Gal80p?
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Represses the function of the activator.
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In yeast galactose metabolism, what is the Gal4p
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Bound to an UAS and acts as an activator.
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What is responsible for removal of repression?
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Binding of galactose to Gal3p and the subsequent binding of Gal3p to Gal80p which results in Gal80p not binding Gal4p and the removal of Gal80+Gal3p to the cytosol.
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What is meant by the modular structure of the transactivators?
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They have regions that are DNA binding and transactivation domains that bind to other proteins.
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What are the different domains of a steroid hormone receptor?
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-Hormone binding domain
-DNA binding domain via Zn finger -Transactivation domain which interacts with co-activators |
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How can phosphorylation modulate transcription?
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DNA Binding Activity
Nuclear Translocation (i.e restrict to cytoplasm or brought to nucleus) |
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What do forms of alternative RNA processing?
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Alternative polyadenylation and splicing
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What proteins are generated from the same gene based on whether they are expressed in the thyroid or the brain? What allows for this divergenece?
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Cacitonin in Thyroid
CGRP in Brain Alternate polyadenylation and splicing |
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What enzyme cleavages dsRNA?
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DICER
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stRNA
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a class of miRNA used during development.
st = small temporal |
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What's the fate of mRNA that forms perfect base pairing with siRNA?
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Degradation
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What is the fate of an mRNA that is imperfectly bound to a siRNA?
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Translational inhibition, but can also be degraded.
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