Lecture 12 - Control of Gene Expression (Ch 8) Flashcards
Proteins that all cell types have are called
housekeeping proteins
Of the genes a cell has, how many of the genes would a typical differentiated cell express?
About half
Cells from an adult cow or carrot can be de differentiated True or False?
True
What can change gene expression? Give an example
External signals like hormones and enzymes can turn a gene off or on- i.e. hormones like cortisol
In bacterial transcriptional regulation, what do bacterial promoters bind to and what is it called?
Bacterial promoters bind RNA polymerase using the sigma factor unit
In transcriptional regulation, what type of promoters are used for eukaryotes?
Eukaryotic promotors bind general transcription factors, that promote binding of RNA polymerase
Regulatory DNA sequences can act on their own, true or false?
False- transcription regulator proteins have to BIND onto DNA sequences
How do transcription regulator proteins BIND onto DNA sequences?
noncovalent interactions, in the major groove, and to intact DNA double helix
How do transcription regulator proteins increase their contact area, making them stronger and more specific?
They bind as dimers
What’s the difference between transcription regulatory sequences and transcription promoter sequences?
One affects levels of RNA produces, and the other affects where transcription starts
How are transcription switches typically regulated?
Via food sources (available or not)
What happens to the trp
operator when there are high levels of tryptophan?
The trp operon is NOT made (not transcribed, basically) because trp binds to a repressor and activates it, so that means more tryptophan is not made
What happens to a trp operon when there are low levels of tryptophan?
The trp operon is MADE (it is transcribed) because the repressor is not activated, so that means it can make more tryptophan
The promoter is the middle part of the operator? True or false? What does the promotor do and what does the operator do?
False- the operator is a part of the promoter; operator is a region of DNA that overlaps with or lies just downstream of the RNA polymerase binding site (promoter). That is, it is in between the promoter and the genes of the operon.
The repressor is always present in the cell for trp, True or False? What mechanism does the repressor use?
True, but it is not always activated; it uses feedback inhibition
What does it mean to use feedback inhibition? Using the trp example
The trp repressor, for example, gets controlled by trp itself
What 2 things is the lac operon controlled by?
The lac repressor and the CAP activator
What happens when glucose is present near a lac operon and lactose is not? What about when lactose IS?
Even if there is lactose, the lac operon will use the glucose because it likes it more :) buttt if lactose is NOT there and glucose is, then the lac repressor binds to the operator and operator is not transcribed
What happens in a non-glucose environment where lactose is present?
If lactose is present and glucose is NOT, then the operon is turned on. CAMP will also bind on CAP site. (ask about this)
What happens if a lactose is not there, and glucose is not there either?
If both are not there, cyclic AMP binds to the CAP binding site ANDDD the repressor is free to bind to the mRNA meaning no operon is transcribed
CAMP concentrations increase when? what do they do?
when glucose goes down, they metabolise sugars other than glucose
What are eukaryotic activators called? How far away do they have to be?
Enhancers; they can work from 1000s of nucleotides away
What binds the activator AND the general transcription factors so that they can work together and promote transcription?
Mediator protein complexes
Where does the chromatin remodeling complex attach itself to? What does it modify?
It attaches near the TATA box, and what is does is that it covalently changes the histone part of nucleosomes
