RNA synthesis Flashcards
1
Q
What subunit directs the E.coli RNA polymerase to the correct transcription initiation sites?
A
sigma
2
Q
transcription
A
conversion of DNA into RNA
3
Q
difference of RNA
A
use ribose sugar
no thymine but uracil
single stranded but can fold
4
Q
mRNA
A
messenger
template for protein synthesis
heterogeneous length - average
5
Q
rRNA
A
ribosomal
major component of ribosome
6
Q
tRNA
A
transfer
carries amino acid in activated form to ribosome
7
Q
snRNA
A
small nuclear - in RNA splicing
8
Q
miRNA
A
micro
around 21 bases
bind to mRNA promoting degrade/inhibit their translation
9
Q
how RNA is produced
A
copying strand of DNA as template - direct transcription 5’ to 3’ direction
10
Q
producing other side
A
coding strand - 5’ to 3’ has same sequence as the RNA
11
Q
catalyst for RNA synthesis
A
enzyme RNA polymerase
using rNTPs, release pyrophosphate
12
Q
nucleotides
A
attached to 3’ -OH from 5’ to 3’ direction
13
Q
DNA Duplex
A
around 17 base pairs
unwound
14
Q
length of RNA-DNA hybrid duplex
A
8bp long
15
Q
contain RNA polymerase
A
alpha*2, 2beta and omega - core enzyme
sigma - direct enzyme to start at initiation site
16
Q
omega
A
stabilises within 5 subunits
17
Q
sigma
A
initiation factor
18
Q
how transcriptional units starts
A
marked by promoters
19
Q
holoenzyme
A
6 subunit 450kDa
RNA polyermase
20
Q
Pribnow box
A
a consensus sequence found at -10 on the non-template strand in bacterial promoter
21
Q
consensus sequence
A
TTGACA
at -35
22
Q
optimal sequence
A
best promoter site for RNA polymerase
23
Q
If Pribnow box had G or C in it
A
harder for RNA polymerase to open up the transcription bubble
24
Q
direction of RNA synthesis
A
5’ to 3’
antiparallel
25
What is formed from RNA synthesis
Transient RNA/DNA duplex
26
RNA polymerase size (how many bp)
able to bind to around 30bp of DNA
27
termination signals
palindromic GC rich regions followed by AT rich region
28
what the new RNA transcript forms
stem and loop
| hair pin structure
29
when RNA transcript forms
RNA polymerase is kicked off
30
protein factor p(pho)
signals for termination are in newly synthesised RNA rather than in DNA template
31
transcription and translation in prokaryotes
occurs at the same time
32
after synthesis in prokaryotes
some RNAs are modified
33
tRNA after synthesis in prokayotes
some bases and sugar are modified
| CCA is added at the 3' end
34
rRNA after synthesis in prokayotes
made as one long molecule - broken up into individual subunits by endo/exonucleases post transcriptionally
35
synthesis in Eukaryotes
more complex due to transcriptional regulation
| has nuclear membrane - separate transcription and translation
36
3 types of RNA polymerase
RNA polymerase I
RNA polymerase II
RNA polymerase III
37
RNA polymerase I role
rRNA - 18s, 5.8s and 28s
38
RNA polymerase II role
mRNA
39
RNA polymerase III role
tRNA and 5s rRNA
40
eukaryotes pre-mRNA processing
addition of poly A tail to 3' end of RNA transcript
| addition of cap to 5' end - 5'-5' triphosphate linked to 7-methyl-G
41
increase in stability and specifies export to cytoplasm
acts as protector role
increase half life
interact binding protein
42
eukaryote Pre-mRNA
contains introns and exons
43
introns
non-coding section
44
exons
coding region
45
order of introns and exons
can not change
46
proteins produced
may contain some exons and not others
47
splicing site
coded by RNA sequence
48
spliceosomes
splices the pre-mRNA
49
importance of spliceosome
allows synthesis of different proteins from one gene - may be cell type specific
50
example fibronectin
component of extracellular matrix
| produced by fibroblast containing exons EIIIB and EIIIA
51
liver cell in example for fibronectin
don't encode the exons which allows fibronectin to be secreted and move freely in blood stream and help clot formation
52
beta-thalassemia number of causes
has 3 ways of this causation
53
beta-thalassemia first causation - change in nucleotide
single nucleotide change - destroying normal splice site - exonskipping
54
beta-thalassemia second causation - extension
activation cryptic splice site - extended exon
55
beta-thalassemia third causation - addition of new
causing of new exons to be incorporated - have extra exons
56
control of transcription
gene expression need to be controlled to form proteins appropriate for tissue and its environment
57
cause of enhancement by activators or blocked by repressors
the interaction of RNA polymerase and a promoter
58
operon
in bacteria
| promoter controls genes in common pathways
59
lac operon - in bacteria
involved n metabolism of lactose
| has lac Z, lac Y and lac A
60
how to stop enzyme production
repressor gene binds to operator sequence - prevents transcription
61
when is gene expressed
when RNA is transcribed into protein
62
constitutive expression
genes expressed all the time
63
regulated expression
genes expressed under certain conditions or time
64
when lactose is present
allolactose binds to repressor protein which prevents binding to operator
therefore genes switched on and protein produced
65
allolactose
inducer of operon
66
can other operons be switched off
yes by other compounds
67
example of other operons
trp operon
68
trp operon
trp repressor binds to operator
in presence of compressors - switch off synthesis
in high presence of tryptophan
69
regulatory gene
transcribed and translated to repressor protein or repressor inducer
70
repressor protein
stop transcription
71
repressor inducer
promote transcription
72
control in eukaryotes complexity
tissue specificity
cell type specificity
development regulation
73
transcription control
DNA packed - due to condensed chromatin
74
modifying histones in transcription control
causes relaxation of region - exposing promoter-proximal element and promoter
75
exposure of ppe and promoter
allows RNA polymerase to bind and transcribe sequence
76
enhancers
found further up stream
| binds to different transcription factor - bind to regulatory sequence close to start site
77
DNA being able to fold back allows
formation of different forms to regulate gene expression of particular genes down stream
78
advantage of DNA folding back to form different loops
help provide tissue selection and cell type
79
Basal transcription factor
common in most genes
80
function of Basal transcription factor
bind to promoter
| such as TATA and CCAAT box
81
Regulatory transcription factor
specific for particular gene - unique
| cell type/ developmentally regulated
82
Regulatory transcription factor function
bind to ppe and enhancer
83
ppe
promoter-proximal element
84
miRNA function
regulate gene expression
85
characteristics of miRNA
small non-coding DNA - 21-25 nucleotide
86
how miRNA is synthesised
as a precursor from nuclear DNA and processed into miRNA in nucleus and cytoplasm
87
human genome encode for miRNA
>1000 miRNA
88
function of miRNA
base pairing complementary sequences in mRNA
| silencing specific mRNA and repressing protein translation
89
miRNA expression
in element close by such as introns
90
miRNA processing
- form pri-miRNA using RNA pol II forming stem loop structure
- processed by Drosha and Pasha - trim different components to form Pre-miRNA
91
miRNA processing out of nucleus
- using Dicer to form miRNA/ antisense miRNA duplex
| which then binds to coding mRNA = rapid degradation
92
after processing
- interfering RNA induced in silencing complex
| - targeting mRNA by relying on complementary base pairing
93
product of targeting mRNA
cleave off the target RNA
translation repression and then destruction of RNA
formation of heterochromatin on DNA (target RNA being transcribed)
