Review of Prokaryotic Gene Expression Flashcards
List two examples of types of cells that can be created through undifferentiated stem cells.
Neuron and Red Blood Cells
How is prokaryotic transcription regulated? What is the name of the enzyme?
It is controlled by a simple mechanism that controls transcription by RNA polymerase
How many RNA polymerases are in eukaryotes?
Three
What kinds of proteins recognize promoter elements (-10, -35)?
Sigma factors.
What is the function of sigma factors when they recognize promoter elements?
They load RNA polymerase at the start site.
Describe General Transcription Factors (Eukaryotes) and their function.
They are involved in a process of recognition of promoter elements and assembly of pre-initiation complex, then load the RNA polymerases.
Name the two “things” responsible for the loading and release of RNA polymerase?
Activators and repressors
The lac operon is a good example of a _____________?
Regulated prokaryotic promoter. The Lac operon and Trp operon are both promoters regulated by activators and repressors, specifically the lac operon repressed by lac I and activated by CAP.
What activates the lac operon to bind it next to a promoter and recruit the RNA polymerase?
An activator protein (CAP) - Catabolite Activator Protein
What is the lac operon repressed by?
A repressor protein (Lac Repressor)
Describe the level of mRNA transcription with low lactose and high glucose (low cAMP).
No mRNA transcription. The lactose must fill in the spaces of the repressor in order to move it away.
Describe the level of mRNA transcription with high lactose and high glucose (low cAMP).
There is low transcription
Describe the level of mRNA transcription with high lactose and low glucose (high cAMP).
There is high transcription. cAMP activates cAMP and lactose represses the repressor so it does not sit on the DNA so that it can be transcribed to mRNA.
Where does RNA polymerase bind too? What position?
-10 position relative to the transcription initiation site.
RNA polymerase requires what kind of factor to initiate transcription? What position does this lay on?
Requires a sigma factor. The sigma factor associates with the -30 position. The -10 and the -30 DNA elements act as basal elements found in promoters.
Is CAP an activator or repressor?
Activator. It binds to the CAP site.
Where does the lac l repressor bind too?
The lac repressor binds to the “operator” binding site instead of lactose. It replaces the operator in the operator binding site.
What happens when the lac repressor binds to the binding site?
The lac repressor takes the place of the operator and RNA polymerase cannot begin the transcription process and therefore no mRNA transcription occurs.
Where does lactose bind do?
Lactose binds to the Lac repressor. Usually, Lac I will bind to DNA downstream of the transcription initiation site and prevent transcription by RNA polymerase.
When there is (+) lactose and (+) glucose (low cAMP), describe the level of transcription.
Low (minimal) transcription when there is high lactose and high glucose (low cAMP).
What is CAP activated by?
CAP is activated by cAMP.
When is cAMP produced?
cAMP is produced in the absence of glucose and presence of lactose.
Where does CAP bind to and what happens?
CAP binds to DNA upstream of the transcription initiation site and stimulates the recruitment of RNA polymerase.
Describe the level of transcription when there is high cAMP.
High transcription.
In the absence of glucose (high cAMP, CAP binds to the promoter) and the presence of lactose (Lac I does not bind to the promoter) the Lac operon is _______.
The lac operon is EXPRESSED.
What is the TRP promoter regulated by?
Activators and repressors.
If tryptophan is limiting in the cell, transcription proceeds to ____________. mRNA for the expression of enzymes for synthesis of tryptophan are produced.
Proceeds to the END OF THE OPERON.
If the concentration of tryptophan is high, transcription is arrested (soon/far) __________ after initiation. Is mRNA produced?
Soon. No mRNA is produced.
