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16 Cards in this Set

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  • Back

What doc ells control to respond appropriately and efficiently to environmental conditions?

1. Gene expression

2. Enzyme activity

Very basic process from DNA to Protein

DNA --(transcription)--> mRNA --(translation)--> Protein

AUG= start codon where translation starts

UTR= where translation ends

sigma factor function

attaches tot he core enzyme and helps RNAP recognize the promoter and initiation site

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

What makes a weaker promoter?

worse match with consensus seq.

--> extra proteins are needed to turn on transcription

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

What do repressors do?

bind to specific DNA seq and block tx of downstream genes


(End product of biosynthetic pathways)

corepressor + repressor ---| transcription


Arg = corepressor binds to repressor to inhibit tx


(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


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)

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

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)

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

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

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

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