Flashcards in Chapter 12 Questions Deck (17)
What are the levels of gene regulation?
DNA methylation and changes in chromatin structure, the level of transcription, mRNA processing, the regulation of mRNA stability, the level of translation, and post translational modifications.
What is transcription such an important gene regulation level?
Because it limits the production of a protein very early in the process.
Why is the regulator gene not considered part of the operon?
It has its own promoter and is transcribed into a short mRNA which is translated into a small protein.
When does transcription take place in positive inducible operons?
When an inducer becomes attached to and activates the regulatory protein.
How is the concentration of cAMP regulated?
It is inversely proportional to the level of available glucose. Low concentrations of glucose stimulate high levels of cAMP.
What is catabolite repression?
Type of positive control of the lac operon. The catabolite activator protein (CAP), complexed with cAMP, binds to a site near the promoter and stimulates the binding of RNA polymerase.
In the trp operon, what happens happens in the absence of tryptophan?
It cannot bind to the operator and transcription takes place.
How does chromatin structure change to allow for transcription to take place?
The structure changes so that the DNA becomes more accessible for transcription factors and RNA polymerase to bind.
How is histone acetylation important in gene regulation?
Its importance is demonstrated in the flowering plant, Arabidopsis thaliana.
What happens when DNA is heavily methylated?
Transcription is repressed.
How do transcription activator proteins affect transcription?
By interacting with the basal transcription apparatus.
How does an enhancer affect the initiation of transcription at a promoter really far away?
The transcriptional regulator proteins bind to the enhancer and cause the DNA to loop out, bringing the promoter and enhancer close to each other so that the transcriptional regulator proteins are able to interact directly with the basal transcription apparatus at the core promoter.
How does an insulator work?
If it lies between the enhancer and the promoter, it blocks the action of the enhancer. If it lies outside the region of the two, it has no effect.
How is transcription is eukaryotic genes regulated if they are not organized into an operon?
They are able to respond to the same stimulus because they share short regulatory sequences in their promoters or enhancers.
How does the poly A tail effect mRNA stability?
When the poly A tail is degraded beyond a critical limit, the 5' cap is removed and the mRNA is degraded from the 5' end.
How do siRNA and microRNA regulate gene expression?
Cleavage of mRNA, inhibition of translation, and inhibition of transcription.