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16 Cards in this Set
- Front
- Back
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regulation of gene expression in prokaryotes is in response to _
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environmental conditions (metabolic needs)
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what is an operon
-what does it contain |
cluster of genes that encode proteins necessary to perform a coordinated function
-promoter, operon, structural genes |
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where is the operator located
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within the promoter sequence
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for Lac operon, who are inducers, who are repressors
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inducer: lactose, allolactose, cAMP-CAP
repressor: glucose |
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what are cis-acting and trans-acting elements
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cis: sequence region located upstream of gene cluster
trans: molecule that binds to cis-region |
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what are the 3 structural genes for the lac operon
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lac Z: B-galactosidase (lactose to glucose and galactose)
lac Y: permease (entry of lactose into bacterial cell) lac A: transacetylase (removes waste products from lactose digestion) |
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what happens to lac operon in presence of allolactose
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allolactose binds to repressor, causing conformation change, increasing transcription of lac operon
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relationship btwn glucose and cAMP
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inverse relationship
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how does cAMP regulate lac operon
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cAMP-CAP complex binds just above promoter in lac operon, acting as an activator to increase RNA poly activity, transcribing lac genes
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what is the repressor of the lac operon system
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lacI makes repressor to bind to operator (O-region)
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what are the 2 differences in Trp operon compared to lac operon
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-repressor region located somewhere else in genome
-operator contained entirely within promoter sequence |
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in trp operon, how many structural genes, what occurs when transcribed
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5
chorismic acid to tryptophan (production of Trp) |
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how does trp affect trp operon
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acts as corepressor, binding to repressors and increasing their affinity for the operon
(absense of trp increases trp operon activity) |
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what is attenuation in trp operon
-what does it contain |
controls transcription of trp operon after RNA poly has initiated synthesis
-two UGG UGG (trp) codons -self-complementary sequences for stem-loop formation -string of U's at 3' end |
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how does attenuation work trp operon
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absence of Trp: ribosome stalls at trp codon, allowing 2-3 stem loop structure formation, allows transcription to continue
presence of Trp: ribosome moves past region 1, does not allow 2-3 stem-loop, transcription stopped |
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which organisms does attenuation not occur
-also regulates synthesis of _ |
eukaryotes because transcription and translation are spatially separated
-other amino acids |
