e. LEC 1 + 2 Slide Deck Flashcards
Which enzyme regulates gene expression in prokaryotes? Is this the same in Eukaryotes?
a) RNA polymerase
b) No in eukaryotes have three different kinds of RNA Polymerases
What are the 3 elements that help initiate transcription of the RNA polymerase in prokaryotes? Describe each.
- -35/-30 = where the sigma-factor associates w/ the DNA
- -10 = where the RNA pol binds to DNA
- +1 (start site) = where transcription starts
In prokaryotes, there are proteins called sigma-factors that are used to load the RNA polymerase onto the start site. What are these promoters called in eukaryotes?
GTF = general transcription factors
What 2 proteins regulate the start and stop of transcription? Indicate which one does what.
- activator = start
- repressor = stop
What proteins regulate
the activator/repressor? provide an example.
the operon for example the lac operon in which the [lac] regulates transcription.
How does the activator encourages transcription and the repressor discourage it?
- Activator = binds to the promoter protein
- repressor = winds the DNA to prevent the RNA pol from transcribing it
Which type of operon is used during prokaryotic transcription initiation vs elongation? How does [high] vs [low] of each affect the activators and repressors?
initiation = lac operon
a) high [lac] = repression of transcription
b) low [lac] = activation of transcription
elongation = trp operon
a) high [trp]= repression of transcription
b) low [trp] = activation of transcription
What is the purpose of gene control in Eukaryotes?
to make sure that the proper genes are being expressed in the proper cells at the proper time
T or F - unlike prokaryotes eukaryotes transcribe DNA that has been wrapped into chromatin
F - While DNA in eukaryotes are packaged in chromatin there needs to be a mech to open that chromatin in order to allow for those genes to be activated/transcribed
T or F - single cellular eukaryotic organisms exist
T - yeast is a great example of this
Describe a nucleosome
DNA wrapped around a histone protein
Describe epigenetic regulation
this is the regulation of DNA caused by changes in the environment.
T or F - while epigenetic markers can change the expression of certain genes as a result of exogenous changes it cannot be inherited as the DNA itself remains the same.
F - it can be inherited
Describe the difference b/w euchromatin and heterochromatin
- E = where genes are unwound and active
- H = where genes are tightly wound and inactive
When staining a eukaryotic cell it shows that heterochromatin is darker than euchromatin. Why is this?
This is b/c heterochromatin is densely packaged DNA that is rich in transposons, centromeres, and telomeres.
Describe the following terms wrt heterochromatin
a) transposons
b) centromeres
c) telomeres
a) repetitive non-coding DNA
b) pt where two chromosomes are attached
c) the protective ends of chromosomes
Fill in the blanks for this RNA chart
What are the 2 main subunits for prokaryotic RNA polymerases? Eukaryotic Pol? What is the purpose of these subunits?
Prokaryotes = beta + beta prime (B and B’)
Eukaryotes = RPB1 + RPB2
These subunits help load the RNA pol onto the DNA and provide it a channel for the transcribed RNA to escape.
Describe the fxn of subunit RPB1 in eukaryotic RNA pols
this subunit is the clamp domain of the Pol. It allows the RNA pol to latch onto the DNA and is then closed by a bridge
Describe homology
similarity
In eukaryotes, scientists have attempted to crystalize all three types of RNA pol however it was found that Pol II was too unstable to do so. ANS the following questions wrt this instability’
a) What is the name of the domain that is making pol II so unstable
b) What subunit is this domain in RPB1 or RPB2
c) Name the 7 AAs that encode this domain.
a) Carboxy-terminal domain = CTD
b) RPB2
c) Tyr-Ser-Pro-Thr-Ser-Pro-Ser (YSPTSPS)
T or F - the sequence that encodes CTD in eukaryotes repeats a total of 52 times.
F - it repeats 26 times for all eukaryotes except mammals in which it repeats 52 times
Name the sequence of 7AA’s that encode the CTD. Which one of the AA’s mentioned is special? how?
Tyr-Ser-Pro-Thr-Ser-Pro-Ser
Ser is special b/c it is phosphorylated when the transcription phases transition from the initiation phase to the elongation phase
What are the common features among all sequences of 7 AA’s w/in the CTD? Explain.
All the AA can be phosphorylated easily. This means it can gain a phosphate group from an ATP as a means of gaining NRG
