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16 Cards in this Set
- Front
- Back
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What doc ells control to respond appropriately and efficiently to environmental conditions? |
1. Gene expression 2. Enzyme activity |
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Very basic process from DNA to Protein |
DNA --(transcription)--> mRNA --(translation)--> Protein AUG= start codon where translation starts UTR= where translation ends |
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sigma factor function |
attaches tot he core enzyme and helps RNAP recognize the promoter and initiation site |
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What makes a stronger promoter? |
A better match of promoter sequence with the consensus sequence for a sigma factor --> yields more binding by the sigma factor and more transcription of the gene |
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What makes a weaker promoter? |
worse match with consensus seq. --> extra proteins are needed to turn on transcription |
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What do accessory transcription factors do? |
Promote or repress transcription of specific genes Know when a protein is active Act like dimers and bind to direct/ inverted repeats on DNA |
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What do repressors do? |
bind to specific DNA seq and block tx of downstream genes |
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Corepressor |
(End product of biosynthetic pathways) corepressor + repressor ---| transcription Ex: Arg = corepressor binds to repressor to inhibit tx |
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Inducer |
(specific enzyme substrate that block action of repressor proteins) inducer--| repressor ---| tx inducer + repressor----> tx Ex. Lac repressor stops tx of lac operon unless lactose is present |
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Activator |
positive regulator recognize specific DNA seq in the promoter coactivator + activator ----> tx Ex: Mal needs mal activator protein AND maltose (activators can increase affinity for promoter by providing extra binding contacts for RNAP) |
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How did ppl find out which system was working between activator+coactivator & inducer+repressor |
We study utilization of raffinose (RafA) by a bacterium RafA produced only when raffinose is present in growth medium |
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RafA experiment Part 1 |
-> make pasmid where rafA promoter drives expression of GFP (only when raff is present in medium) -> mutagenize with a transposon -> plate on a mixture of sugars (Gray colonies do not express GFP due to Tn insertions) |
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RafA Experiment Part 2: Plating Tn mutants |
-> Plate them on medium w/ glucose+raffinose then replica plate on glucose ONLY -> Those that glow green on glucose have Tn that allow GFP expression when it should be OFF |
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Repressor- corepressor case: Mutations on arg tx |
1. Pt. mutation in operator, doesn't let repressor bind 2. Repressor KO 3. Pt. mutation in repressor, doesn't let corepressor bind |
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Repressor- inducer case: Mutations on lac tx |
1. Repressor KO 2. Pt. mutation in operator, doesn't let repressor bind 3. Pt mutation in repressor doesn't let inducer bind |
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Activator- coactivator case: Mutations on mal tx |
1. Pt. mutation in activator binding site 2. Activator KO 3. Point mutation in activator protein no longer binds coactivator |
