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43 Cards in this Set
- Front
- Back
What processes are controlled in the regulation of gene expression?
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transcription and translation
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What are genes that encode proteins that function throughout most of the life cycle of an organism? |
housekeeping genes |
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What is a small molecule that stimulates the synthesis of an inducible enzyme? |
inducer |
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What is a gene whose expression level can be increased by a regulatory molecule? |
inducible gene |
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What is a gene that encodes a protein whose level drops in the presence of a small molecule?
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repressible gene |
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What occurs when the binding of a regulatory protein to DNA inhibits the initiation of transcription? What is that protein called?
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negative transcription control repressor |
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What occurs when the binding of a protein to DNA promotes transcription initiation? What is that protein called?
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positive transcriptional control activator |
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Where are activator-binding sites often located?
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upstream of the promoter |
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What generally facilitates RNA polymerase binding? |
activator
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How are repressors and activators controlled? |
small effector molecules bind noncovalently (allosteric regulation) |
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What is the inactive form of a repressor protein? When does it become active? |
aporepressor when the corepressor binds to it |
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What are the genes that code for nonregulatory polypeptides? |
structural genes
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What are often lined up together on DNA and a single, polycistronic mRNA carries all the messages?
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structural genes |
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When is the lac repressor responsible for inhibiting transcription? |
lactose |
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What are small effector molecules whose presence increases the level of specific enzymes? |
inducers |
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What are genes that are turned "off" until turned "on?" |
inducible genes |
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What are genes that are "on" until turned "off?" |
repressible genes
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Is the lac operon an inducible or repressible gene? |
inducible |
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How does the lac repressor inhibit transcription? |
binds to O1 and one additional lac operator site and bends the DNA in the promoter region |
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What is the segment of DNA in an operon to which the repressor protein binds? |
operator |
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Where are operators usually located? |
overlaps or is downstream of the promoter |
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Why are many promoters of regulated genes and operons considered "leaky?" |
there is always some low, basal level of transcription |
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What is the sequence of bases in DNA that contains a promoter and one or more structural genes and often an operator or activator-binding site that controls their expression? |
operon |
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What do the three genes of the lac operon code for? |
Beta-galactosidase
Beta-galactoside permease Beta-galactoside transacetylase (unknown function) |
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When is the lac operon expressed at high levels? |
in the presence of lactose but not glucose |
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What reaction does Beta-galactosidase catalyze?
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lactose to allolactose |
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What is the inducer of the lac operon?
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allolactose
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What functions in a global regulatory network that allows E. coli to use glucose preferentially over all other carbon and energy sources by a mechanism called catabolite repression? |
catabolite activator protein (CAP) |
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What regulates the lac operon in response to the presence or absence of glucose?
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CAP |
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What is the tryptophan operon regulated by?
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trp repressor
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When does the tryptophan operon function and why? |
When tryptophan is not present and must be made de novo from precursor molecules. |
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What is the function of tryptophan when tryptophan levels increase? |
corepressor, binding the repressor and activating it |
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What does the repressor-corepressor complex attach to, blocking transcription initiation? |
operator |
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What is the ara operon regulated by? |
AraC
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What is the function of AraC when arabinose is not present?
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one molecule binds aral and another binds araO2, the two interact and cause DNA to bend, blocking transcription |
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What is the function of AraC when arabinose is available? |
activator
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Is the trp operon an example of positive or negative transcriptional control? |
negative |
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Is the ara operon an example of positive or negative transcriptional control? |
both
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Are most biosynthetic enzymes inducible or repressible?
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repressible |
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What are two common motifs of the DNA-binding domains of regulatory proteins?
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helix-turn-helix zinc fingers |
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How do DNA-bound repressor proteins inhibit the initiation of transcription? |
by either blocking the binding or preventing the movement of DNA polymerase |
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Are enhancers components of bacterial operons? |
no
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What is the domain of each subunit of the lac repressor protein? |
helix-turn-helix
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