Chapter 11: Gene Regulation Flashcards
What are general purpose (housekeeping) genes
Genes that are needed by all cells but are not expressed at all times of the cell cycle
What are specialty function genes?
Genes that are needed for response to specific environmental changes of for specialized cell (tissue) functions
What are the types of control points in gene regulation?
Transcriptional control, processing control, transport control, translational control, post-translational control
What regulations fall under transcriptional control?
DNA accessibility (1) and transcription initiation (2)
What regulations fall under Processing Control?
RNA processing (3)
What regulations fall under Transcriptional Control?
nuclear export (4) and mRNA stability (5)
What regulations fall under Translational Control?
translation (6) – consists of initiation, elongation & termination
What regulations fall under Post-translational Control?
protein modification (7) and protein degradation (8)
Between what steps does transcriptional control occur?
DNa and RNA transcript
Between what steps does RNA processing control occur?
RNA transcript and mRNA
Between what steps does RNA transport control occur?
mRNA inside the nucleus and mRNA outside the nucleus (in the cytosol)
Between what steps does translational control occur?
mRNA and protein
Between what steps does protein activity control occur?
protein and inactive protein
What control types do prokaryotes have?
transcriptional control, translation control, and protein activity control
Where does gene expression begin?
the promoter, where transcription is initiated
What happens in selective gene transcription?
a decision is made about what genes to activate
What is constitutive expression?
constant gene transcription
What do regulatory proteins do?
control the expression of other genes; most genes are under the control of multiple regulatory proteins
Where does the majority of regulation occur?
At transcription
Negative regulation
Binding of a repressor protein to DNA preventing transcription; transcription initiation can occur in the absence of the repressor protein
Positive regulation
activator protein binds to DNA and stimulates transcription; transcription initiation low in the absence of the activator protein
Prokaryotes generally _______ of a protein when it is not needed
stop synthesis
How do prokaryotes stop synthesis (5 ways)
repress mRNA transcription
Hydrolyze mRNA, preventing translation
Prevent mRNA translation at the ribosome
Hydrolyze the protein after it is made
Inhibit the protein’s function
What are the energy sources for E coli?
Glucose (preferred), lactose (requires synthesis of proteins to take it in and break it down)
What proteins are involved in the uptake and metabolism of lactose?
galactoside permease, galactosidase, galactoside transacetylase
What does galactoside permease do?
A carrier protein that moves lactose into the cell
What does galactosidase do?
An enzyme that hydrolyses lactose
What does galactoside transacetylase do?
transfers acetyl groups to certain galactosides
What is the inducer for the lac operon?
Lactose converted into allolactose
When lactose is added, then removed, ______ persists for a while but ____ levels drop instantly. Why?
protein persists but mRNA drops. This is because proteins are relatively stable and mRNA are not
Lactose metabolism in an example of _________ through ____
inducible gene regulation through transcription
What are two separate genetic modules in lactose metabolism? What do they code for?
1) A gene (i) coding for the lac repressor protein; a negative regulator of the lac operon
2) the lac operon codes for 3 structural proteins needed for the utilization of lactose
The structural genes needed to utilize lactose are ____ on the E coli chromosome, share a single _____ and are encoded on a single _____ with different sites of ________
adjacent
promoter
transcript
translation initiation
What is the operon under coordinate control from?
The promoter and operator
What is the promoter?
the region of DNA where RNA polymerase binds and initiates transcription
What is the operator?
the region of DNA between the promoter and the structural genes that is bound by the lac repressor
What does a repressor protein do when the inducer is absent?
binds to the operator to block transcription of the operon (by preventing RNA polymerase from initiating at the promoter)
What inactivates the repressor? What happens as a result?
An inducer; the inactive repressor is unable to bind the operator so RNA polymerase can bind at the promoter and initiate transcription
What type of system is lactose metabolism?
An inducible system
How does a repressor protein express negative control
by blocking transcription when bound at the Operator; the repressor able to bind in the absence of the inducer (lactose and operon is turned off (repressed)
How do inducers show negative control?
they change repressor proteins so that they are unable to bind at the Operator; the operon is available for transcription; when the inducer (lactose) is present operon is turned on (expressed)
What happens in terms of protein synthesis when both lactose and glucose are present?
the lac operon can transcribe, but transcription is not activated. Only a small amount of protein is synthesized
What are the two types of operons?
Inducible (catabolic) operons (ex. lac operon)
Repressible (anabolic) operons (ex. trp operon)
Inducible operon
the substrate (inducer) for a catabolic enzyme binds to repressor and changes it so it cannot bind the operator – transcription is on
Repressible operon
end product of the anabolic pathway acts as a co-repressor to allow repressor to bind operator and repress transcription – transcription is off
In trp, the enyzyme produces ____ which is also the ____ exemplifying the _____ operon
tryptophan
co-represser
repressible
What are operons
Genes that encode proteins that are involved in the same metabolic pathway
T/F Sequences at and near the promoter control transcription initiation through interactions with regulatory proteins
F; Sequences at and near the promoter control transcription initiation through interactions with transcription factors
Describe initiation of transcription in Eukaryotes
TFIID binds to the TATA box; other transcription factors bind to form a transcription complex. The transcription factors must assemble on the chromosome before RNA polymerase is recruited to the promoter
Where do transcription factors act?
eukaryotic promoters
What are eukaryotic promoters?
regions of DNA where RNA polymerase binds and initiates transcription
What are the two important sequences in RNA transcription
recognized by RNA polymerase
TATA box
where DNA begins to unwind and expose the template strand
How does genetic control of sex determination work>
The default development is female; there is an SRY transcription factor that is only on Y alleles, so when a Y is present, SRY is present and starts encoding for a male
What does SRY bind to
Response element
When is gene expression coordinated?
If the different genes have the same regulatory sequences that bind the same transcription factors
What does the SRY protein do to DNA?
It binds DNA at the sequence 5’-ATAACAAT-3’ and bends the DNA in that region to change the openness of chromatin
Is enhancers a positive or negative regulator? Silencers?
Enhancers are positive; silencers are negative
What is the first thing to bind to the promoter that all other transcription factors bind to?
Basal transcription apparatus
What do enhancers and silencers do to DNA?
They loop the DNA and the enhancer/silencer binds to the basal transcription apparatus and all transcription factors that are with it
When does DNA form condensed chromatin and how does that affect transcription?
When DNA is wrapped around histones, proteins form condensed chromatin, which is inaccessible for transcription
