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
