Mod 6 Ch. 15 Flashcards
Combinatorial control refers to the phenomenon that..
The combination of many factors determines the expression of any given gene
A regulatory transcription factor protein typically contains ___ that binds to the ___ of the DNA.
An alpha helix, major groove
A bidirectional enhancer has the following sequence:
5’-GTCA-3’
3’-CAGT-5’
Which of the following sequences would also be a functional enhancer?
5’-TGAC-3’
3’-ACTG-5’
Regulatory transcription factors can be modulated by..
- the binding of small effector molecules
- protein-protein interactions
- covalent modifications
A chromatin-remodeling complex may..
- change the locations of nucleosomes
- evict nucleosomes from DNA
- replace standard histones with histone variants
According to the histone code hypothesis, the pattern of histone modifications acts like a language that..
Influences chromatin structure
Which of the following characteristics is typical of a eukaryotic gene that can be transcribed?
The core promoter is found in a nucleosome-free region
Transcriptional activation of eukaryotic genes involves which of the following events?
All of the above
- changes in nucleosome locations
- changes in histone composition within nucleosomes
- changes in histone modifications
How can methylation affect transcription?
- it may prevent the binding of regulatory transcription factors
- it may enhance the binding of regulatory transcription factors
- it may attract the binding of methyl-CpG-binding proteins, which inhibit transcription
The process in which completely unmethylated DNA becomes methylated is called..
De novo methylation
Insulators may exert their effect by..
- acting as a barrier to changes in chromatin structure
- blocking the effects of neighboring enhancers
Which of these levels is the most energy-efficient way to regulate gene expression?
Transcriptional regulation, because a cell avoids wasting energy making RNA or protein
Explain how an alpha helix is able to function as a recognition helix in a transcription factor protein.
It can bind into the major groove of DNA and recognize a specific sequence of bases
If a repressor prevents TFIID from binding to the TATA box, why does this inhibit transcription?
RNA polymerase will not be recruited to the core promoter
When an activator protein interacts with mediator, how does this affect the function of RNA polymerase?
Causes mediator to phosphorylate CTD, which causes RNA polymerase to proceed to the elongation phase of transcription
Explain why the glucocorticoid receptor binds next to the core promoter of some genes, but not next to the core promoter of most genes.
Binds only next to genes that have a GRE by their core promoters
How might nucleosome eviction affect transcription?
May allow certain proteins access to binding to particular sites in the DNA
Describe two ways that histone modifications may alter chromatin structure.
May directly affect the interaction between histones and the DNA, or they may affect the binding of other proteins to the chromatin
Why is an NFR needed at the core promoter for transcription to occur?
So that activators can recognize enhancers and then the preinitiation complex can form
Explain why histone eviction is needed for the elongation phase of transcription.
Because RNA polymerase cannot transcribe through nucleosomes
What is the difference between be novo methylation and maintenance methylation?
De novo methylation occurs on unmethylated DNA
Maintenance methylation occurs on hemimethylated DNA
Why are insulators important for gene regulation in eukaryotes?
They prevent one gene from regulating a neighboring gene. This allows each gene to control its own regulation
