Control of Gene Expression Flashcards
If all cells from the same organism contain the same DNA, how can they be so different?
Via Gene Expression; Different cell types produces sets of protein
Why do cell differentiation arise?
Because cells make and accumulate different sets
of RNA and protein molecules: that is, they express different genes.
Describe the cloning experiment that proves why different cell types contain the same DNA
- Nucleus is taken out from a skin cell in an adult frog
- The nucleus was injected into a frog egg with an empty nucleus
- Tadpole continued to develop
Why is the regulation of transcription paramount?
To ensure that no unnecessary intermediates are synthesized.
What is the significant of having a regulatory DNA sequence to where the RNA polymerase initaite?
control transcription initiation; switch the gene on or off
What must DNA sequence require to regulate transcription?
Transcription regulator
What does transcription regulator do?
Act as a switch to control transcription
Why is the major grooves of a DNA important for transcription?
Transcripter regulatory protein can interact with the genetic information at the major groove
What is an operon?
Cluster of genes that are transcribed together to give a single messenger RNA
What happens to the operon when tryptophan concentration is low in bacteria?
The operon is transcribed, making RNA that synthesize the amino acids
What does transcription regulator do to prevent transcription?
It binds to the operator on the promoter which prevents access of RNA polymerase to the promoter, preventing transcription.
What happens to the genes when tryptophan is low?
RNA polymerase binds to the promoter and transcribes the five genes of the tryptophan operon; operon is on and can be transcribed
What happens to the genes when tryptophan is high?
Repressor protein becomes active and binds to the operator where it blocks the binding of RNA polymerase to the promote; operon is off and cannot be transcribed
What does activator protein do?
bind to a nearby regulatory sequence and make contact with the RNA polymerase, helping it to initiate transcription
Why might an activator protein be important for transcription?
the promoter may fails to initiate transcription efficiently.
What does lac operon do?
Encodes proteins required to import and
digest the disaccharide lactose. I
When would a lac operon shut off?
In the absence of lactose
When is cAMP activated?
In the absence of lactose
In the absence of lactose, which is activated/deactivated?
Lac operon is deactivated
cAMP is activated
When is lac operon only activated?
In the presence of lactose
In the absent of glucose
How can gene activation at a distance in eukaryotes?
Because DNA can loop, the activator protein can come in contact with the transcription initiation complex which may affect transcription rate
How does gene affecting local chromatin structure regulate transcription via chromatin remodeling complex?
Render the nucleosomes more accessible to other proteins in the cell. TATA box may be exposed more, promoting transcription
What is combinatorial control?
Multiple DNA-binding proteins can be involved in gene
regulation
Eukaryotic cell uses a committee of transcription regulators to control each of its genes, how can it rapidly and decisively switch whole groups of genes on or off?
A single transcription regulator can be decisive in
switching any particular gene on or off by completing the combination needed to activate or repress a gene; the same protein can complete/regulate the combination for several different genes.
