Chapter 12: The Control of Gene Expression Flashcards
(43 cards)
1
Q
Proteasome does what?
A
- chops up polypeptide if something is wrong ( one way of going about controlling gene expression)
2
Q
Organization of a bacterial operon: What is a promoter?
A
- DNA sequence that promotes transcription
3
Q
Organization of a bacterial operon: How does a promoter, promote transcription?
A
- it is where the polymerase will bind and or the activator to help out in the promoter region all to enhance the probability of transcription to occur.
4
Q
Organization of a bacterial operon:
Operator region? L> repressor protein?
A
- it is located somewhere in the gene itself it can be in the promoter by the promoter…and generally it is a sequence of DNA that will bind to a repressor protein turning it off…aka preventing transcription. Generally the repressor protein is a protein that was transcribed and translated on its own somewhere else to one and bind to this regulatory region
5
Q
Lac operon
- it is what kind of an operon?
A
- inducible
6
Q
Lac operon
- lactose used by bacteria in the absence of?
A
-glucose
7
Q
Lac operon
- What genes are involved?
A
- Lac Z, Lac Y, Lac A
8
Q
When is the lac operon transcribed?
A
- decreasing levels of glucose in the bacterial medium causes a cellular response
- increase in cAMP+ - intracellular cAMP binds to CAP(catabolite activator protein) and this complex binds to DNA:
- CAP binding site
- RNA polymerase is able to bind to promoter IF lactose is present in the medium
- lactose will bind to and inactivate the lac repressor ***
- dual operator control….CAP acts as an activator and the negative control: the lac repressor that turns it off.
9
Q
Inner workings of the Lac operon:
- lactose binds to?
A
- active lac repressor
- RNA polymerase is now able to bind to promoter
10
Q
Control Region of the Lac Operon:
- Describe the structure of it
A
- Promoter region= cAMP-CRP binging site, RNA Polymerase binding site and the first part of the operator.
- operator region
L> mRNA?
- I gene
- Z gene
11
Q
Lac operon:
- Describe induced state
A
- structural genes (Z, Y, A)
- transcription of those via RNA polymerase
- mRNA is produced
- goes through translation via polyribosomes
- produces enzymes
- the enzymes can utilize lactose via catabolic pathway causing the concentration of lactose to fall as it is degraded…the operon will enter a repressed state due to this
12
Q
Lac Operon:
- describe the repressed state
A
- as concentrations of lactose go down via it being degraded by the enzymes produced from the lac operon …the operon will enter a repressed state
- this state blocks transcription via something blocking the operon from being transcribed
13
Q
Eukaryotic Gene Repressor proteins:
- three scenarios ?
A
- competitive DNA binding
- fight between activator (repressor for binding site (overlap). - Masking activation surface
- repressor/activator both bind, but activator surface is pressed - Direct interaction with general transcription factors
14
Q
Silencing Genes:
-____ level of control
A
- transcriptional
15
Q
Silencing Genes:
- Now active genes are?
A
- silenced
16
Q
Silencing Genes:
- methylation of?
A
- DNA
- CG sequence: CCGG or GGCC
- inherited in progeny cells
17
Q
Silencing Genes:
- what checks the CG sequence?
A
- maintenance methylase checks CG sequence
18
Q
Silencing Genes:
- binding of ___ that recognize ___.
A
- proteins
- methyl C
19
Q
Silencing Genes:
- Complexes?
A
- Chromatin remodelling complex, histone complex bind/activate.
20
Q
Silencing Genes:
- 1/100000 nucleotides ___. Is this universal in eukaryotes?
A
- methylate
- no
21
Q
Silencing Genes:
- The replication fork, methylates ?
A
- daughter strand by copying methylation on parent strand.
22
Q
Silencing Genes:
-Symmetrical sequence?
A
- methylates after transcription…ONMT1 protein travels with
23
Q
Alternative Splicing:
-this allows you to obtain what?
A
- different proteins from a single RNA transcript
24
Q
Alternative Splicing:
-shorter antibodies result released in blood (ex:IGM) - hydro_?
A
hydrophilic
25
Alternative Splicing:
-They are longer in?
- membranes of infected cell, hydrophobic
26
Alternative Splicing:
- RNA editing?
- RNA made, maybe processed, enzyme only affects
27
Alternative Splicing:
-functions?
- New splice sites
- Adinine
- new stop codons - amino acid substitutions
28
Negative Translational Control:
- ___ sequence in prokaryotes
- Shine-dalgarno sequence
- six conserved nucleotides (GGAGGA)
- upstream AUG
- correctly position RNA initiating codon with small ribosomal subunit
29
Negative Translational Control:
- involves what?
- Blocking the shine dalgarno sequence by a translational repressor protein.
30
Negative Translational Control:
- EIF2?
- eukaryotic activation (initiation) factor brings in initiator tRNA, phosphorylated, can't bring in initiator
31
Negative Translational Control:
- Translational ____ in eukaryotes.
- repressor proteins
- RNA binding protein -blocks translation at 5' end
32
Negative Translational Control:
- Ex of translational repressor proteins in eukaryotes.
- AConitase bind to hairpin loop preventing translation
33
Inner workings of the Trp Operon:
- tryptophan is what?
34
Inner workings of the Trp Operon:
- How do bacterial cells acquire trp?
35
Inner workings of the Trp Operon:
- where is the operator located?
- smack in the middle of the promoter
36
Inner workings of the Trp Operon:
- how is the operon repressed?
- if trp is in the environment ..it comes along and binds to the represor that is not active at the time and goes and finds its spot on the DNA to stop it from synthesizing more (represssed state)
37
Trp Operon :
-explain the repressed state and active staate
- repressed state:
active represor with trp bound to it attaches just before the structural genes ( E, D, C, B, A) not allowing RNA polymerase to read the non-coding strand to produce an mRNA template
- its biosynthesis is halted..tryp concentration falls as it is utilized causing it to enter an active state
2. Active state:
- inactive repressor does not bind to the non coding strand
-- RNA poly binds and transcription occurs producing an mRNA strand
- mRNA undergoes translation producing enzymes which break something down to produce tryptophan
38
Repressible operon (example fully explained)
Repressible Operon
- Trp operon
- corepressor (tryptophan) binds to inactive repressor which attaches to the non coding strand just before the structural genes (E, D, C, B, A) blocking transcription since RNA poly does not have access
- this causes trps biosynthesis to be halted..tryp concentration falls as it is utilized... causing the operon to enter an active state from its formally repressed state
- inactive repressor cannot bind to the non coding strand.... RNA poly has access to it and mRNA is transcribed
- mRNA is transsalted producing enzymes which react with something providing an end product of tryptophan
39
Induceable Operon? (example fully explained)
1. Lac operon
- induced state:
- an inducer (lactose) binds with an active repressor causing it to become inactive thereby it cannot access the non coding strand
- RNA poly transcribes the structural genes (Z,Y A)
- mRNA is produced
- mRNA is transalted producing enzymes
- the enzymes break down lactose into a uilizable compound
- as cocnentrations of lactose decline as it is degraded .....an active repressor binds to the non coding strand not allowing further transcription of the operon since RNA poly cannot access it now.
40
Enhancers are??
41
Enhancers:
-what binds to them?
L\> explain what they do
- gene regulatory proteins bind to the enhancer .... which is a distal promoter element...
- GRPS
- activates transcription of a gene/aids it
- GRPS bound to enhancer intreat with protein and RNA polymerase at promoter
-
42
Enhancers:
- insulator?
43
Enhancers:
- explain the two complexes involved
1. chromatin remodeling complex and histone modification complex are co-activators that will help in the process of regulating transcription..enhance it with repsect to DNAs level of compaction ...if bound too tight it wont transcribe
