Regulation of Gene Expression Flashcards
(98 cards)
1
Q
operons
A
clusters of metabolic genes with related functions
2
Q
expression of the gene clusters is controlled by…
A
an operator region embedded into the promoter
3
Q
operons are transcribed as
A
polycistronic mrna molecule
4
Q
enhancing transcription
A
activatory factors bind to the promoter
5
Q
inhibiting transcription
A
repressor proteins bind to the operator blocking access to rna polymerase
6
Q
lac operon
A
regulates lactose metabolism
7
Q
expression of lac operon genes are controlled by…
A
glucose
8
Q
what happens when glucose is present
A
repression of lac operon and transcription is off
9
Q
what happens when glucose is absent
A
cAMP levels rise binds to CAP and binds to lac promoter, expression of lac operon and transcription on
10
Q
operator
A
negative regulatory site bound to repressor protein
blocks rna polymerase
11
Q
CAP binding site
A
positive regulatory site bound to CAP (catabolite activator protein)
12
Q
CAP function
A
binds to rna polymerase enabling transcription
13
Q
what happens when lactose is present
A
inactivates lac repressor
14
Q
what happens when lactose is absent
A
lac repressor binds to operator that overlaps with promotee inhibiting rna polymerase transcribing lac operon
15
Q
tryptophan operon
A
encodes proteins involve tryptophan synthesis
16
Q
trp operon is regulated by…
A
trp repressor
it is a sensor for the tryptophan levels
17
Q
low tryptophan levels
A
expression of trp opreron
18
Q
high tryptophan levels
A
repression of trp operon
19
Q
rna polymerase I
A
large rRNA
20
Q
rna polymerase II
A
mrna and mirna
21
Q
rna polymerase III
A
small rRNA and tRNA
22
Q
how do rna polymerase (eukaryotes) bind to promoter
A
basal transcription factors
23
Q
common core promoter elements
A
BRE TATA INR DPE
24
Q
core promoter function
A
recruits general transcription factors and position rna polymerase II complex at transcription start site
25
TFIID
recognises TATA and regulates DNA-binding to TATA box promoter
26
TFIIB
positions rna polyII at transcription start site
27
TFIIE
recruits and regulates TFIIH
28
TFIIH
unwinds double stranded dna at transcription start point and phosphorylates C-terminal domain of rna poly.II and releases it from promoter
29
inducible transcription factors
recognises specific sequences within wider promoter and enhancer regions of genes
30
how are inducible transcription factors usually activated
from external stimuli i.e. changes in environment
31
different ways inducible tf are activated in cell
protein synthesis
ligand binding
covalent modification (phosphorylation, ubiquitination)
addition of second subunit (dimersation)
32
nf-kb activation
external stimulus activates kinase complex
phosphorylates ikb protein
k-48 linked ubiquination and proteasomal degradation
activates nf-kb and trnaslocates to nucleus
33
inducible tf binds to..
specific short dna sequences in promoter regions of genes
34
inducible tf contans an activation domain that
regulates activation of transcription when bound to dna
35
inducible tf mediates transactivation wen
either ineracting with rna poly.II complex or by recruiting chromatin remodelling enzymes
36
when inducible tf are activated they....
translocate to the nucleus
37
the edge of each base pair in dna contains..
a distinctive pattern of h-bond donors acceptors and methyl groups
38
hwo tf binds to dna
amino acid side chains interact with specific dna bases
dna-binding proteins bind with dna through h-bonding ionic bonding and hydrophobic interactions
39
dna-binding proteins
helix-turn-helix
zinc fingers
leucine zippers
40
helix-turn-helix
they bind forming dimers and bind to major groove of dna
41
zinc fingers
bind as dimers and binds to major groove of dna
42
leucine zippers
two helices held together by hydrophobic interactions
sit on dna like a clamp
43
b-sheet structural motifs
double stranded b-sheet with amino acid side chains reads info on the surface of the major groove of dna
44
chromatin function
condenses long dna into more compact structures
45
chromatin
complex of dna with histones
46
chromatin condensing
less accesible for transcription factors
47
chromatin loosening
transcription factors more accesible and enables transcription
48
euchromatin
composed of 30nm fibres and looped domains
49
euchromatin are associated with...
actively expressed areas of the genome
50
heterochromatin
highly condensed compact dna
51
heterochromatin are associated with....
non-expressed areas of the genome
52
tyoes of heterochromatin
constitutive and faculative
53
constitutive heterochromatin
highly concentrated in specific regions (telomeres and centromeres)
has no coding region
54
faculative heterochromatin
can covert between heterochromatin and euchromatin
55
drosphila- expression of red eye colour
heterochromatin is blocked from entering the euchromatin regions by a barrier made out of dna sequences
56
drosphika - expression of white-speckled eye colour
barrier sequenced reomved and heterochromatin spreads to euchromatin region
57
during interphase chromatin is
is in its loosely state
58
during prophase
chromatin condenses and chromosomes become more visible
59
acetylation and methylation occur on
lysine residues
60
phosphorylation occurs on
serine residues
61
acetylation of histones is often associated with...
gene expressing
62
acetylation function
removes the positive charge on the lysine residues decreasing the affinity of the dna-histone complex
63
histone acetylation is carried out by..... and removed by.....
histone acetyltransferases
histone deacetylases
64
histone acetylation creates.....
binding sites for certain chromatin remodelling enzymes
65
methylation of histones is often associated with....
gene silencing
66
histone methylation is carried out by... and removed by....
histone methyltransferases
histone demethylases
67
why acetylation and methylation cannot occur at the same time
they are both competing reactions and cant be on the same lysine at the same time
methylation - repressing
acetylation - expressing
68
histone code hypothesis
the transcription of genetic info encoded in dna is regulated by chemical modifications
69
histone code readers determine either...
chemical modification or specificity
70
histone code readers funcrion
mediate the downstram consequences of histone modifications or recruit other effector proteins
71
effector proteins
enzymes that can alter chromatin structure or nucleosome position in an atp dependent manner
72
bromodomains
recognises aceylated lysine
73
chromodomain
recognises methylated lysines
74
dna methylation in eukaryotes...
regulates gene expression in 5' position of cytosine
75
cpG islands
GC-rich regions
promoter regions of genome
76
cpg methylation
results in gene repressing by blocking promoters
77
dna methyltransferases
transfers a methyl group from s-adenyl methionine to the 5th carbon of a cytosine residue to form 5mC
78
state of dna in globin gene promoter in embryo
unmethylated
79
state of dna in globin gene promoter in embryo
unmethylated
80
state of dna in globin gene promoter in fetus
activates fetal globin genes -> methylated dna
81
x-inactivation/lyonization
since female xx chromosomes carries twice the amount of x-linked genes than males one or two are randomly inactivated early in embryonic development
82
what happens to the inactivated x chromosome
it condenses into a compact structure called a barr body and remains inactive throughout the lifetime of the cell
83
x-inactivation is commonly....
randomly distributed unevenly
84
epigenetics
the study of how cells control gene activity without changing the dna sequence
85
epigenetic changes are...
modifications of dna that regulate gene turning on or off
86
epigenetic changes results in....
inheritable phenotypes that are not due to a change or alteration to the dna sequence
87
epigenetic mechanisms constrain expression by....
adapting regions that either associates with gene silencing or gene activity
88
after dna replication chromatin are
reinstated by reader-writet complexes
89
the expression of imprinted genes ... between the maternal and paternal allele
differs
90
genomic imprinintg
ppl inheriting two copies of their genes from mother and father and only one is acitve
91
luciferase reporter assay
promoter region of interest clones into plasmid vector that contains luciferase gene
can quantift promoter activity by measuring luciferase activity
92
chromatin immunprecipitation
determines tf binding to promoter, rna poly.II binding to promotwrs and presence of histone modifications
cross-link bound prtoeins to dna
use antibody to immunoprecipitate protein of interest
remove and detect bound dna with pcr
93
mrna processing
5' cap added to start and 3' poly-A-yail added to the end
splicing - introns removed and exon ligated together
94
5' cap
a modified G nucleotide that protects transcript from being broken down
95
poly-A-tail
allows mature mrna to be exported from the nucleus and translated into protein by ribosomes in cytoplasm
96
5' utrs
involved in translation
97
3' utrs
responsible for the stability of mrna
98
splicing
the removal of introns and ligation of exons by splicesomes
catalysed by snRNPs
