Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Biochem BLOCK 3 > Transcription > Flashcards

Transcription Flashcards

(79 cards)

Start Studying
1
Q

RNA polymerase action (general features of transcription)*

A
  • begins transcription without a ‘primer’
  • reads the template strand from 3’ to 5’
  • synthesizes the RNA transcript 5’ to 3’ using ribonucleotides (NTPs)
  • recognizes transcription termination signals
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Transcription begins with

A
  • RNA polymerase identifying a gene’s promoter region
  • interacting with the DNA template strand
  • initiating synthesis of a complementary, antiparallel RNA transcript
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

When does transcription end

A

When a termination signal is reached

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What strand is read during transcription?

A

Template strand

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

DNA coding strand sequence compared to RNA transcript sequence

A

Identical except RNA has Us instead of Ts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How are are base sequences (in DNA) numbered?

A

By giving the first base to be transcribed a +1 designation with +2, +3, etc. in the 3’ direction (downstream to the right)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How are the upstream DNA bases to the left, in the 5’ direction designated?

A

-1, -2, -3, etc

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Holoenzyme

A

Core enzyme + sigma factor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Core enzyme

A 
4 subunits 
-two alpha subunits
-1 beta subunit
-1 beta-prime subunit 
  =a2BB
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What kind of enzyme activity does core enzyme have?

A

RNA polymerase activity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is sigma factor required for?

A

Recognizing and binding promoter sequences

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Sigma factor

A
  • different sigma factors recognize different types of promoter sequences
  • recruits the core enzyme to the DNA promoter
  • dissociates from the core enzyme after the transcription begins
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Initiation of transcription in prokaryotes

A

-scanning and recognition of promoter sequence cues by the holoenzyme trigger transcription initiation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Promoters

A

Contain two consensus sequences that are recognized by sigma factor

  • TATA box
  • -35 sequence
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

TATA box in prok

A

Consensus sequence of 6 nucleotides (TATAAT) sometimes called the pribnow box, ~7 nucleotides upstream from the +1 transcriptional start site (~-7)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

-35 sequence in prok

A

Second consensus sequence (TTGACA) ~ 35 bases upstream (-35) from the +1 transcriptional start site

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Elongation in transcription of prok

A

Transcription beings at the +1 transcriptional start site, sigma factor is released and the core enzyme continues

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What does elongation create in transcription of prok

A

A temporary ‘melt’ between the double stranded DNA-forming a transcription bubble
-supercoils may be relieved by the action of topoisomerases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Net reaction of prok RNA synthesis (transcription)

A

Addition of a ribonucleotide to the growing RNA chain, and the release of pyrophosphate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is pyrophospate cleaved by?

A

Pyrophosphatase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Cleaving of pyrophosphate by pyrophosphatase

A
  • irreversible coupled reaction

- 2 high energy bonds are cleaved

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

2 termination mechanisms of prokaryotic RNA synthesis (transcription)

A
  • Rho dependent termination

- Rho independent termination

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Rho dependent termination

A

Requires an additional protein

-rho factor: displaces the DNA template strand from RNA polymerase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Rho factor

A

Displaces the DNA template strand from RNA polymerase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Rho independent termination
Requires G-C rich step loop followed by a poly-U stretch | -causes RNA polymerase to dissociate
26
Prokaryotic mRNA can be...
Polycistronic
27
Polycistronic
One mRNA can code for several proteins
28
Polycistronic mRNAs
Often code for multiple enzymes in the same biosynthetic pathway
29
Eukaryotic mRNAs are always
Monocistronic
30
Rifamipin (rifamyin)*
- antibiotic - binds to prokaryotic RNA polymerase and prevents transcription initiation/elongation - used to treat tuberculosis
31
Prokaryotic synthesis of tRNA and rRNA
Similar to the model for eukaryotes, except in prokaryotes the same RNA polymerase produces all types of RNA
32
Why is eukaryotic DNA highly condensed (chromatin)
To allow gene transcription the genes must be exposed
33
Euchromatin
- Less condensed | - more accessible to RNA polymerases
34
Acetlyation of histone H1
Causes the chromatin to revert to nucleosomes (bead on a string)
35
Heterochromatin
- appears more dense | - DNA is relatively inaccessible due to highly condensed structure
36
DNA in herterchomatin
Highly methylated
37
What is the foundation of epigenetics
DNA methylation | -twins with same genes, some mutations can result in the way its methylated in expressed between the twins
38
RNA polymerase I (euk)
Transcribes precursors to rRNA in the nucleolus
39
RNA polymerase II (euk)
Transcribes the precursor to mRNA (hnMRNA) in the nucleoplasm (some snRNAs as well)
40
RNA polymerase III (euk)
Transcribes tRNA precursors (also small rRNA and some snRNAs)
41
RNA pol II recognizes what two consensus sequences in eukaryotes
- TATA box (Hogness box) | - CAAT box
42
TATA box (Hogness box)
- similar yo prokaryotic TATA box | - approximately 25 nucleotides upstream (-25)
43
CAAT box
- eukaryotes | - appproximately 70 nucleotides upstream (-70)
44
Eukaryotic transcription elongation
Essentially the same as prokaryotic RNA syntheiss
45
Termination of euk transcription
Requires a signal not well understood in euk
46
rRNA synthesis and processing
- not actually expressing a gene - three rRNAs are transcribed as a single larger precursor (by RNA pol I in the nucleolus) - individual rRNAs cleaved apart by RNases - prokaryotic rRNA synthesis is the same as in eukaryotes - instrumental in making ribosomes
47
tRNA synthesis and processing
-RNA pol III in in the nucleoplasm
48
RNA polymerase III in tRNA synthesis and processing
- removal of intron loops - trimming of the 5' and 3' ends - base modifications - addition of the 3'-CCA sequence***
49
Eukaryotic mRNA synthesis
Spatially and temporally separated from translation
50
Transcription takes place (euk)
In the nucleus
51
Translation takes place (euk)
In the cytoplasm
52
Eukaryotic mRNA processing
Processed extensively (hnRNA to mRNA)
53
When do prokaryotic mRNAs being translation?
Before transcription finishes
54
Shine Delgarno sequence
Tells ribosome to start translation in prok
55
Euk promoter regions
``` CAAT box (-70) TATA box (Hogness box) (-25) ```
56
Prok promoter region
``` TATA box (Pridnow) (-10) -35 sequence ```
57
Untranslated regions in prokaryotes and eukaryotes (UTRs)
Both have a 5' and 3' UTR
58
Coding region in eukaryotes and prokaryotes
Eukaryotes have introns and exons (monocistronic) | Prokaryotes don't have that
59
5' capping in eukaryotic mRNA
- Addition of a 7-methylguanosine to the 5' end of the mRNA-5' to 5' linkage - serves as a ribosome recognition signal and stabilizes mRNA (protects from nuclease degradation)***
60
3' poly A tail in Euk mRNA
The 3' terminus contains a polyadenylation signal- a special enzyme (poly A polymerase) adds a variable stretch of adenin residues (~40-200)
61
What kind of signal does the 3' poly A tail of eukaryotic mRNA serve
Serves a signal for transport out of the nucleus, and stabilizes the mRNA from nuclease attack
62
Is the 3' poly A tail terminu encoded in the gene (of euk mRNA)
No, but the SIGNAL sequence is encoded, but the additional A's are not
63
Intervening sequences in euk RNA synthesis
Introns
64
Expressed sequences in euk RNA synthesis
Exons
65
Removal of introns
Must be removes from the coding region for proper translation
66
Splicing
The removal of introns and the jointing of exons by snRNPs
67
SnRNPs
Are composed of snRNAs and a group of proteins
68
What are the snRNPs combined with?
Primary transcript from the spliceosome | -this is the molecular machine that performs the splicing reaction
69
Lariat
Excised intron
70
Splice sites
Have very specific sequences (mutations at these sites can cause incorrect splicing)
71
Exons join together
During splicing to form mature mRNA
72
How many intron sequences can eukaryotes contain?
Between 0 and 50
73
Alternative splicing of hnRNAs
Joining of different exons together o form different mRNAs
74
What does alternative splicing permit?
The production of proteins with some common domains, but the over all function of the protein is different -gene is same though
75
Systemic lupus erythematosus
Causes butterfly rash - observed in late-teen females - patient produces antibodies that recognize host proteins, including snRNPs
76
After all processing events, mature eukaryotic mRNA is transported where?
Cytoplasm
77
What mushroom genus accounts for 95% of all mushroom fatalities?
Genus amantia
78
Amanita phalloides
The death cap mushroom
79
Alpha-amanitin
From amanita phalloides mushroom | -binds to RNA polymerase II-inhibits mRNA synthesis

Biochem BLOCK 3 (12 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions