Gene Regulation
What are the two forms of control for bacterial gene regulation?
Positive (CAP + cAMP)
Negative (repressor)
DNA replication equivalent to Denaturation step in PCR
Helicase in DNA replication has the same function as Heat (95C) in PCR
Give an example of a signal that requires its receptors to be inside of the cytoplasm.
Any steroid hormone (estrogen, testosterone, progesterone)
Any hydrophobic molecule that can diffuse through the plasma membrane
What is the role of p53?
p53, a tumor suppressor protein, can monitor for DNA damage and triggers apoptosis to eliminate damaged cells. This prevents cancer development.
You identify an E. coli strain that transcribes the lac operon even in the absence of lactose. What mutations could have lead to this phenotype?
A mutation in operator that disrupts repressor binding. A mutation in repressor that causes it to not bind to operator
Explain the difference between leading strand and lagging strand of DNA synthesis
The leading strand is synthesized continuously whereas the lagging strand is synthesized in pieces that ligase links together later
Given the structure of cAMP, why would it not be advantageous for a cAMP receptor to be located in the cytoplasm of a cell?
cAMP is a polar/hydrophilic molecule, so it's unlikely to cross the plasma membrane. It cannot interact with a cytoplasmic receptor.
Would active MPF promote or inhibit entry into S-phase?
Active MPF would disrupt entry into the S-phase.
Your e.coli is grown in a medium of glycerol. What lac operon regulation mechanism(s) is/are at work?
In Glycerol, cAMP and CAP are going to be bound to the CBS. Positive regulation is active.
In Glycerol, repressor is going to be bound to the operator as no lactose is present. Negative regulation is also active.
When attempting to amplify one region of DNA, you accidentally use primers that are too short and an annealing temperature that is much lower than normal. What results would you get?
Primers would bind to additional sites in the DNA/be less specific.
We would end up with additional pieces of DNA
Explain the role of Adenylyl cyclase in the signaling pathway of adrenaline/epinephrine.
When activated, Adenylyl cyclase catalyzes the formation of ATP to cAMP, which can then activate pkA and further enzymes in the pathway.
What happens to proteins that have been ubiquitin-tagged?
They are sent to a proteasome where they are degraded and recycled
Why is mRNA stability more important in Eukaryotic gene regulation than Prokaryotic gene regulation?
In prokaryotes, transcription and translation are done right after one another. As soon as mRNA is transcribed, it is translated. There is no opportunity for mRNA stability to influence the rate of translation.
A eukaryotic cell evolves to use DNA primers. How could this be advantageous to the organism?
The cell would not need to use DNA Poly 1 to convert RNA primers to DNA. Since creating an enzyme takes energy, this cell would have an advantage as it doesn't need to create DNA poly 1.
What needs to happen for an actin microfilament to get shorter?
Rate of depolymerization must be greater than the rate of polymerization
There must be plenty of available ADP-actin
How could a protein block CDK activity?
- block the active phosphorylation of CDK
- phosphorylate the inactive site of CDK
- block the active site of CDK so it can't be phosphorylated
- block dephosphorylation of inactive site of CDK
You discover a eukaryotic cell with a mutation that prevents chromatin acetylation. How would this affect gene expression?
Chromatin acetylation is not working, therefore gene transcription cannot happen. This mutation would result in lower rates of gene transcription + expression.
DNA strands are held together by H-bonds. How would the DNA sequence affect rate of replication?
DNA replication would slow down in a sequence of mostly G-C's because they have more H-bonds between them than A-T's
How could a cell block/slow actin polymerization?
Many options:
decreasing availability of ATP-G Actin
express a protein that blocks G-actin from being added to actin filament
increase rate of microfilament severing
block transduction of signal that is initiating actin polymerization
Which could lead to decreased levels of p53 in a normal cell?
a. increased histone acetylation of p53 gene
b. addition of ubiquitin to the p53 protein
c. decreased transport of p53 mRNA out of the nucleus
d. increased binding of a transcription repressor to the p53 promoter
e. decreased polyadenylation of p53 mRNA
b, c, d, e are correct.