L8: Regulation of Prokaryotic Transcription Flashcards
1
Q
Genes are often organized as _____
A
operons
2
Q
Prokaryotic genes are _____–one promoter direct the synthesis of a mRNA that can encode more than one proteins
A
polycistronicc
3
Q
Polycistronic
A
One promoter direct the synthesis of mRNA that can encode more than one proteins
4
Q
Operon
A
An arrangement of genes in a contiguous linear array
5
Q
An arrangement of genes in a contiguous linear array
A
Operon
6
Q
In an _____ a continuous strand of mRNA carries the message for a related series of enzymes (polycristonic mRNA)
A
operon
7
Q
Why are genes organized into operons?
A
- genes encoding enzymes in a common pathway can all be induced simultaneously
- known as “coordinate control”
- one mRNA expresses multiple proteins
8
Q
Coordinate control
A
- type of control where genes encoding enzymes in a common pathway can all be induced simultaneously
- one mRNA expresses multiple proteins
9
Q
- type of control where genes encoding enzymes in a common pathway can all be induced simultaneously
- one mRNA expresses multiple proteins
A
coordinate control
10
Q
Transcription of the structural genes is controlled by _____ protein
A
repressor
11
Q
_____ sequence determines first level of regulation
A
Promoter
12
Q
Promoter sequence determines first level of regulation
A
- weak promoters have poor consensus sequences and initiate transcription infrequently
- strong promoters generally have good consensus sequences and initiate transcription often
- many promoters are regulated by addition regulatory proteins as well
- repressors inhibit transcription initiations (Lac repressor)
- activators increase transcription initiation (CAP)
13
Q
_____ promoters have poor consensus sequences and initiate transcription infrequently
A
weak
14
Q
_____ promoters generally have good consensus sequences and initiate transcription often
A
strong
15
Q
weak promoters have _____ consensus sequence and initiate transcription _____
A
poor
infrequently
16
Q
strong promoters generally have _____ consensus sequences and initiate transcription _____
A
good
often
17
Q
Repressors
A
- inhibit transcription initiation
- block transcription initiation
- ex: lac repressor
18
Q
Activators
A
- increase transcription initiation
- speeds up transcription
- ex: CAP
19
Q
_____ inhibit transcription initiation
A
repressors
20
Q
_____ increase transcription initiation
A
activators
21
Q
An example of repressor
A
Lac operon
22
Q
An example of activator
A
CAP
23
Q
3 levels of transcription
A
- basal level
- repressed
- activated
24
Q
_____ _____ proteins can facilitate these distal interactions
A
DNA bending
25
Repressors usually block transcription initiation by:
- interfering with RNA polymerase binding
| - preventing open complex formation
26
Lac operon consist of _____ genes under the control of a single operator
3
27
3 genes of lac operon
1. lacZ
- encodes beta-galactosidase, an enzyme tha tcatalyzes the hydrolysis of lactose
2. lacY
- encodes the lactose permease, required for transport of lactose into the cell
3. lacA
- encodes a transacetylase enzyme that transfers an acetyl group from acetyl-CoA to Beta-galactosides
- the cell can use lactose as an energy source by producing the enzyme beta-galactosidase to digest lactose into glucose and galactose
28
lacZ
- encodes beta- galactosidase
| - an enzyme that catalyzes the hydrolysis of lactose
29
beta-galctosidase
enzyme that catalyses the hydrolysis of lactose
30
enzyme that catalyzes the hydrolysis of lactose
beta-galactosidase
31
lacY
- encodes for lactose permease
| - required for transport of lactose into the cell
32
lactose permease
required for transport of lactose into the cell
33
required for transport of lactose into the cell
lactose permase
34
lacA
- encodes a transacetylase enzyme
| - transfers an acetyl group from acetyl-CoA to Beta-galactosides
35
transacetylase enyme
transfers an acetyl group from acetyl-CoA to Beta-galactosides
36
transfers an acetyl group from acetyl-CoA to Beta-galactosides
transacetylase enzyme
37
encodes for Beta-galactosidase
lacZ
38
encodes for lactose permease
lacY
39
encodes for transavetylase enzyme
lacA
40
Cell can use _____ as an energy source by producing the enzyme beta-galactosidase to digest lactose into glucose and galactose
lactose
41
Cell can use lactose as an energy source by producing the enzyme beta-galactosidase to digest lactose into _____ and _____
glucose
| galactose
42
High levels of lactose result in _____-_____ production
Beta-Gal
43
High levels of _____ result in Beta-Gal production
lactose
44
Hydrolysis to galactose and glucose sugras = _____ in cell
energy
45
Hydrolysis to _____ and _____ sugars = energy in cell
galactose
| glucose
46
substrate and inducer used in _____ _____ studies
Lac operon
47
Inducer: IPTG
will induce the lac operon but is not metabolized, so its concentration stays constant during an experiment
48
_____ will induce the lac operon but is not metabolized, so its concentration stays constant during an experiment
IPTG
49
Substrate:
Bacterial colonies expressing B-galactosidase turn blue on agar plates containing __-___, which is a substrate for B-galactosidase but is not an inducer
X-gal
50
X-gal
A substrate for B-galactosidase that makes bacterial colonies expressing B-galactosidase to turn blue on agar plates
51
lacI
- not part of the lac operon but codes for repressor
| - has separate promoter and is transcribed independently of lacZ, lacY, and lacA
52
_____ is not part of the lac operon but codes for repressor
lacI
53
Mutations
changes in the normal DNA sequence
54
_____ are changes in the normal DNA sequence
Mutations
55
_____ cells have mutations in the normal DNA sequence found in cells isolated from the wild
Mutant
56
"wild type" sequence
DNA sequence found in cells isolated from natural sources in the wild
57
____ are DNA sequence found in cells isolated from natural sources in the wild
"wild type" sequence
58
Inducible synthesis
synthesis that is turned on by an inducer
59
______ _______ is a synthesis that is turned on by an inducer
inducible synthesis
60
Constitutive synthesis
- synthesis at a constant level in the presence or absence of inducer
- loses all regulatory control of the lac operon
61
_____ _____ is a synthesis at a constant level in the presence or absence of inducer
Constitutive synthesis
62
I- mutants
mutant in I gene, resulting in a defective repressor
63
O^c mutants
mutant in the binding site (operator) for the repressor
64
Mutant in I gene, resulting in a defective repressor
I- mutants
65
Mutant in the binding site (operator) for the repressor
O^c mutants
66
I- and O^c mutants can be distinguished by analyzing _____ _____
partial diploids
67
I- and O^c mutants can be distinguished by analyzing partial diploids
- both result in constitutive expression of B-galactosidase
- since bacteria are haploid, a plasmid can be used to introduce a second copy of the lac operon into the cell
- I- and O^c mutations behave differently in the cis vs. trans arrangement
68
O^c mutation is physically linked to the _____ gene (cis)
Lac Z
69
_____ _____ is the protein product of the I gene
| - it is diffusible within the cell (trans)
Lac I Repressor
70
Widetype situation
lac operon is transcribed only in the presence of an inducer
71
Mutation in the lac repressor gene (lacI) results in _____ _____ because no repressor is made
constitutive expression
72
Mutation in the operator results in _____ _____ because the operator site is lost and repressor can't bind
constitutive expression
73
When the repressor is supplied in trans, _____ is observed again
regulation
74
When operator is supplied in trans, there is _____ ______
no effect
75
lac operon is also under _____ control
positive
76
Glucose metabolism is favored over _____ meabolism
lactose
77
Level of glucose in media is detected by _____
cAMP
78
high glucose = low cAMP = no CAP (low transcription)
low glucose = high cAMP = bring in CAP (high transcription)
79
_____ binds to specific DNA sequences
CAP-cAMP
80
Binding results in a bend in the _____
DNA
81
_____ also interacts directly with the RNA polymerase to stimulate binding to weak promoter sequences
CAP-cAMP
82
RNA polymerase binding at _____ _____ with the help of CAP
lac promoter
83
CAP is recognized by the _____ of polymerase
CTD (carboxyl terminal domain)
84
CAP is _____ which increases transcription
activator
