Miles - Biochemical Control and Gene Regulation I, II, III Flashcards
How does substrate concentration or availability effect pathway?
For many enzyme, Km=physiological concentration–this will keep First Order and respong best to change in Substrate. Cofactors and compartmentalization lso play a role.
In higher organisms can also change quantity and efficiency of enzymes via regulation. (Feedback, inhibition, activation by proteolysis, +/- Phosphate)
What is difference between prokaryote and eukaryote regulation?
Prokaryotes: Gene expression is temporally separated, transcription and translation are coupled
Eukaryotes: Gene expression is temporally and spatially separated. Transcription in nucleus, translation in cytoplasm.
How does regulation of gene expression control enzymatic processes?
Housekeeping: Trancribed in fixed amount, required at all times
Growth Medium: Made is low amounts in response to medium, higher when stimulated
Biosynthesis: Made when endproduct is not present in growth medium, repressed if end product is available
What type of system is the lac operon an example of?
Inducible Enzyme System
During induction of the Lac Operon, what occurs in the following media situations:
Glucos
Lactose
Glucose + Lactose
Glucose = DownDownDown
Lactose = UpUpUp
Glucose + Lactose = Up
What occues when glucose is in the media for the Lac Operon?
Repressor bind to operator to block transcription—NEGATIVE CONTROL
What occurs when lactose is in the media for the Lac Operon?
Inducer binds to repressor to release from operator, RNA polymerase proceeds;
At low glucose cAMP is high and binds to CAP protein, which binds to CAP site—increase RNA polymerase binding to promoter.
Positive Control.
What occurs when Glucose and Lactose are present in the medium for the Lac Operon?
Inducer releases the repressor from the operator, however cAMP is high, so no CAP-cAMP complex forms. Catabolite Repression.
What occurs during a Lac-I mutation?
Repressor unable to bind operator, constitutive gene expression
What occurs during a Operator locus mutation in the Lac Operon?
Operator sequence can bind repressor–constitutive expression
Describe the Jacob and Monod model of enzyme repression?
f the end product is available from the medium, them enzymes of the biosynthetic pathway are not made. If the end product is absent from the medium then the enzymes are made.
What type of regulation is usually used in the anabolic pathway?
Derepression
What must a repressor have complexed to it in order to gain affinity for the operator?
Corepressor
What is the result if end product is not available in Jacob Monod model?
All enzymes are coordinately de-repressed (they are made)
Attenuation
Premature termination of mRNA synthesis
What is the difference in prokaryotic attenuation vs Operon model?
Regulation at variable termination, NOT variable initiation.
Occurs at transcription level
Attenuation;
High AA Concentation =
Low AA Concentration =
High = mRNA synthesis is terminated to prevent enzyme synthesis
Low = mRNA synthesis is completed
How is attenuation regulated?
Secondary structure forming at 5’ end of nascent mRNA; depends on rate of movement of first ribosome to translate message
Histidine Operon is example
How is the Histidine Operon model regulated?
Attenuation (variable termination)
What are the five levels of regulation?
- Genome
- Transcription
Post Transcription:
- RNA processing and export
- Translation
- Post-translation
What type of chromatin is subject to DNase I cutting?
Euchromatin
What are possible control points for gene expression in eukaryotes?
Environmental and Differentiation
It’s a long list, each has their own notecard.
X Chromosome Inactivation
Occurs in females, one X chromosome is methylated and turned off
Lyon Hypothesis
Methylated section of chromosomes are Barr bodied, not identical in all cells
