Topic 10 Flashcards
What does transcription regulation involve in prokaryotes
A single activator or repressor protien
How many rna polymerase to prokaryotes have, where does transcription and translation happen
1 type rna pol
Prokaryotes have no nucleus so in cytoplasm at the same time
Where does mRNA synthesis occur
At the +1 site next to the promoter
Atg (start codon is further down stream)
How does transcription initiation and elongation happen in ecoli
A sigma factor brings the 5 subunit rna pol and positions it at the promoter
Then sigma factor leaves and elongation in 3’ to 5’ direction happens
(New mRNA is 5-3’
What are the two types of termination in prokaryotes
Factor independent termination
Rho dependent termination
What is factor independent termination
Doesn’t need rho protiens
Gc rich dna which is followed by an A rich code makes the gc from a loop and the unstable AAAAAA code causes rna pol to detach from transcript
Gc and au terminate transcription
What is rho dependent termination
The rho factor (protien) see a c rich sequence in the dna and then release rna pol from the template
What are characteristic of bacteria in relation to gene expression
They need to get and break down sugars from the environment, they use it as a carbon source
The conserve energy by only making the enzymes they NEED for improper and metabolism when the sugar is present
They recognize environmental condition (whether lactose present) and respond to them (by activation or repression of genes)
What is the promoter
Dna sequence the rna pol binds to to start transcription
What is the activator where does it bind
What type of regulation is this
Protien that brings the rna pol cooler to the promoter
Binds to the activator binding site
Promotes transcription
Positive
What is the repressor where does it bind
What type of regulation is this
block rna pol from binding to promoter OR block it from moving along the dna
Bind to the operator on dna
Negative
If activator cant bind to activator binding site:
No transcription OR low/basal level of transcription
If repressor can’t bind to operator
If binds , no transcription
No binding so transcription occurs
What is an allosteric effector
Molecules that bind to the allosteric site of regulatory protiens
Some regulatory protien with the effector bind and some without the effector bind
What does the effector help with
Presence/ absence of it can help the cell respond to the environment by changing the conformation of regulatory protiens and helping them bind or not bind
What is the example of effector
Ex. for genes that control lactose metabolism, The effector is lactose
Lactose (the effector) binds to the repressor and prevent repressor from binding.
This cause rna to be made
What is an operon
Linked genes that are controlled by one promoter
All involved in the same function (metabolizing lactose)
Genes are turned into single mRNA
Either all or none of the gene products (enzymes) will be made
What is the lac operon
The operon needed for transport and metabolism of lactose
What are the protein coding genes in the lac operon
ZYA
MAKE
B-galctosidase, permease, transacylease
The protiens are needed for lac metabolism, what do each do
Permease (Y) : transports lactose into cell
Beta galactosidase (Z): changes lactose to allolactose then cleave lactose
What is the “I” gene is the location of the gene important
The gene that encodes (makes) the repressor protein
No, just the protien it make is important
What is transacting elecmwnt
When something effects gene expression of distant genes (on diff dna than itself) as well as nearby genes (on same dna as itself)
What is cis acting element
Affects expression of nearby genes (on same dna as itself)
What are cis acting element examples
What are transacting examples
Operator and promoter
Protiens
What does negative regulation do
Involves only the repressor
Turns lac operon on or off
Makes rna or not
What does postive regulation do?
Involves the activator and fine tunes the expression levels of the lac operon
More/Less expression
Involves the presence of glucose
What happens to the lac operon if there’s no lactose present
Doesn’t need to make metabolizing protiens
Repressor bind to operator, stops transcription, no ZYA made
What happened to the lac operon if lactose is present
Need to make metabolizing protiens
Lactose (inducer) makes allolactose (effector) which attached to repressor and stops is from binding to operator
Rna pol transcribe ZYA
What does noninduced conditions mean
Repressor is non induced, so it’s binds to operator and ZYX made
What does induced conditions mean
Repressor is induced, lactose present, repressor doesn’t bind to Operator, ZYX made
If Z- what does this mean
Inactive Z, no z made no matter what
Non induced, no z
Induced, no z
What is a constitutive mutation ?
Lac operon is on (proteins are made) where the inducer is present or not
Oc : means in non induced condition, protiens still made
What else other than lactose can we use as inducer
IPTG
What is the special thing that happens to make F’ plasmids
When the F factor (HRF) exits the chromosome it came from, it picks up some of the chromosomes dna
The F factor plus the picked up dna is the f’ plasmid.
What is the bacterial cell that has f’ plasmid inserted into it called
Merozygote
(Partial diploid)
Is Oc mutation cis or transacting
Cis, only affect what it’s attached to
If attached to Z+, Z always expressed in no induced and induced conditions
What does I + mean
Repressor is there, regular conditions
What type of mutation is I-, what does it mean
Constitutive
If it’s I-, lac operon is always on, expression in every condition,
Is I+/I- cis or trans acting
Trans acting if present it affects everything , I+ dom over I-
What is iS mutation
Trans or cis
Super repressor, it resist effect of inducer
Affects the allosteric site
So in non induced and induced condition, repressor always bind operator and no expression
Trans
If iS and I+ what’s dominating
Is
Oc is _______to is
Epistatic
Oc masks the effect of Is
Repressor can’t bind beats repressor isn’t affected by inducer
What is the preffered energy source for prokaryotes, why
Glucose because energy capture from it is more efficient
If glucose is there, The cell conserves it energy and resources by reducing expression of the enzymes needed to process lactose
If gluscose it present:
If the lac operon is turned on, it has minimal expression
If glucose not present
If lax operon turn on, Enhanced expression because no glucose so it needs to use lactose
What is the effect of high cAMP
It activate the lac operon (more expression)
High glucose what happens to camp
Low glucose?
Low cAMP because glucose stop conversion of atp to camp, cap doesn’t bind, low lac expression
High camp because conversion isn’t inhibited, cap binds, enhances lac expression
What is cAMP amd CAP
What is the CAP-cAMP complex
Allosteric effector for CAP
CAP is an activator protein, bind to the cap binding site in promoter when also bound to camp
Enhances rna pol transcription
What are two way the lac operon can turn on
Presence of inducer (lactose, IPTG)
Constitutive mutation (Oc or I-)
If glucose and lactose present what happens
If just glucose
If just lactose
Minimal expression of lac operon
No expression of lac operon
Enhance because (camp-cap)
CAP+ AND CAP- are cis or trans?
Transacting
Cap+ dom over CAP-
What does you need for enhanced expression
No glucose and a functional CAP
In the promoter is P- what happens to the operon
Everything down stream of the promoter is gone
