Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Genetics > Transcription > Flashcards

Transcription Flashcards

1
Q

Who proposed the central dogma of biology and when?

A

1956 Francis Crick proposed a fundamental concept in genetics

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

Central Dogma

A 
flow of heredity information	
 DNA provides the code that eventually leads to proteins- DNA does not directly code for proteins 
DNA ---> RNA ---> protein 
DNA- RNA= transcription 
RNA- protein= translation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Transcription

A

DNA is converted to RNA

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

What are the 3 stages of transcription?

A
  1. Initiation
  2. Elongation
  3. Termination
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Describe the basic process of transcription?

A

DNA is converted to mRNA

Uses one strand of DNA (called the template strand) to make single-stranded RNA

The new RNA molecule is synthesised via RNA polymerase

Direction of transcription is 5’-to-3’
 Antiparallel to the template strand

The complementary DNA strand to the template strand is the coding strand (older term no longer used: non-template strand)

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

What is the direction of transcription?

A

Direction of transcription is 5’-to-3’

Antiparallel to the template strand

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

RNA polymerase

A

Pairs template-strand nucleotides with RNA- specific complementary nucleotides

catalyses the formation of phosphodiester bond to join the RNA nucleotide (NTP)
adds the nucleotides to the 3’ end of the growing RNA strand

synthesizes the new RNA strand from the template DNA strand

Complementary and antiparallel nucleotide base-pairing to the template strand

Attaches to a promoter- that is upstream of the gene to be transcribed
Ends transcription at the termination sequence,- which is downstream of the gene to be transcribed (3’ to the end of the coding region)

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

coding strand

A

The complementary DNA strand to the template strand
(older term no longer used: non-template strand)

Same direction (5’-to-3’) and sequence as mRNA, only has T’s instead of U’s

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

Promoters

A

are regions on the DNA template strand that RNA polymerase recognises and initiates transcription (“this is the start of the gene this is where we need to begin”)

are not transcribed but rather direct the RNA polymerase to the correct starting place, the start of transcription

upstream of the gene to be transcribed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Where is DNA transcribed?

A

The DNA is transcribed between the start of transcription region and the termination sequence

nucleus

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

start of transcription

A

the DNA location where transcription of a sequence begins

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

termination sequences

A

Transcription ends
tells RNA polymerase to stop

is downstream of the gene to be transcribed (3’ to the end of the coding region)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Introns

A

are regions that are transcribed but do not code for specific proteins (ie non-coding) and so will get removed before the mRNA is translated

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

Exons

A

are the regions of mRNA that do code for proteins and will remain in the mRNA for translation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are the 4 mains kinds of RNA?

A

Messenger RNA (mRNA): transcription, carries genetic code

Ribosomal RNA (rRNA): translation, part of ribosomes

Transfer RNA (tRNA): translation, carries amino acids

Small nuclear RNA (snRNA): mRNA processing and intron removal

Micro RNA (miRNA) and small interfering RNA (siRNA): regulatory RNA

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

What are some Features of RNA ?

A

Contains 4 ribonucleotides: (made of ribose sugar instead of deoxy)
 Uracil (U) instead of Thymine (T)
 Adenine, cytosine, guanine same as DNA

Hydroxyl (OH) group on 2’ carbon in ribose

Usually single stranded

  • Can form short double-stranded hairpin structures
  • Helps in tertiary protein folding
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

RNA polymerase core

A

(Bacteria)
Protein complex composed of 5 subunits
2 alpha subunits, 2 beta subunits, 1 omega subunit
Binds to a 6th polypeptide called sigma subunit

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

sigma subunit

A

sixth polypeptide that when rna polymerase core attaches to it switches polymerase to the active form- holoenzymee

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

Describe bacterial promoters

A

are double stranded regulatory DNA sequences that bind transcription proteins (RNA polymerase)

In bacteria, 2 promoter regions

although they are double stranded they are written in a single shot hand form that gives the 5’- 3’ sequence of the coding strand

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

What are the 2 promoter regionsin bacteria?

A

Pribnow box sequence (aka -10 consensus sequence) (minus means upstream from gene)

5’-TATAAT-3’

-35 consensus sequence

5’-TTGACA-3’

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

closed promoter complex

A

initial stage of transcription when the RNA polymerase core enzyme and sigma subunit (together form holoenzyme) bind to the promoter consensus sequences,

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

open promoter complex

A

forms when DNA unwinds near the transcription start site to

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

Outline bacterial Transcription Initiation

A
  1. The RNA polymerase core enzyme and sigma subunit bind to the promoter consensus sequences, forming a closed promoter complex
  2. DNA unwinds near the transcription start site to form the open promoter complex
  3. The holoenzyme (RNA polymerase + sigma subunit) progresses downstream to initiate RNA synthesis at the +1 nucleotide on the template strand
    sigma subunit dissociates shortly after transcription initiation and the core enzyme continues transcription
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Outline bacterial Transcription Elongation

A

The core enzyme of the RNA polymerase synthesises RNA until it reaches the termination sequence

As the RNA polymerase progresses, DNA unwinds to allow the template strand to direct RNA assembly
- Progresses at ~40bp/s in the 5’-to-3’ direction

The DNA immediately returns to a helix after RNA polymerase passes by

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Outline bacterial Transcription Termination
Once the polymerase reaches the termination sequence, it is released from the template strand and dissociates from the mRNA transcript mRNA transcript is 5’-to-3’ (same as coding strand of DNA except has U’s instead of T’s) mRNA transcript is complementary and antiparallel to the template DNA strand
26
intrinsic terminators
rho(rho is a type of protein) independent) Dependent on specialized DNA sequences that induce the formation of hairpins (loops) in the RNA Rich in GC nucleotides Stretches of T’s in the coding strand (A’s in the template strand) mean lots of U’s in the RNA (ie polyU tail) which cause the RNA polymerase to slow down and destabilize
27
Rho-dependent termination
Rho protein binds to RNA at the rut site once the rho utilisation site is transcribed Protein causes RNA polymerase to dissociate at the terminator region due to the formation of a stem-loop structure
28
State a difference between bacterial and eukaryotic transcription?
Unlike bacteria which have a single core polymerase, eukaryotes have 3 different RNA polymerases
29
general transcription factors
6 proteins eukaryotic transcription proteins that bind the promoter region to form part of the apparatus that initiates transcription
30
List the different RNA polymerases present in Eukaryotes and function?
RNA polymerase I (RNA pol I): transcribes ribosomal genes RNA polymerase II (RNA pol II): transcribes mRNA RNA polymerase III (RNA pol III): transcribes tRNAs
31
RNA polymerase II
binds to several promoter regions in eukaryotic DNA
32
What are the promoter regions in eukaryotic DNA?
TATA box -> located -25 bases upstream of the transcriptional start site CAAT box -> located -80 bases upstream of the transcriptional start site GC-Rich box -> located -90 or more upstream of the start site Not all genes have all 3 promoter regions....
33
Describe the process of Eukaryotic transcription initiation
TFIID (TATA-binding protein + TBP- associated factor) binds to the TATA box Forms the initial committed complex Other TFs (TFIIA, TFIIB, TFIIF) and RNA polymerase join the initial committed complex TFIIE and TFIIH then join the complex, forming preinitiation complex (PIC) All of these TFs are commonly called general transcription factors (GTFs) Once the PIC is formed, transcription starts at the +1 nucleotide on the template strand
34
silencer sequences
repress transcription Bind to proteins that bend the DNA such that genes get hidden behind the bended segment, thus blocked from RNA polymerase activity
35
Enhancer sequences
Often promoters alone cannot initiate transcription in RNA pol ii are DNA regulatory sequences that increase (“enhance”) gene transcription Bind to specific proteins that interact with proteins bound at promoter regions, forming “bridges” that bend the DNA and links the transcription complex
36
Transcription factors
help bind the RNA polymerase to the DNA promoter regions
37
Chromatin
mixture of DNA + associate proteins (the “spaghetti” state) 
38
TFIID
TFIID (TATA-binding protein + TBP- associated factor) binds to the TATA box Forms the initial committed complex
39
Euchromatin
not densely compacted genetic material, actively transcribed
40
What affects/ regulates transcription in eukaryotes
Chromosome state also affects/regulates transcription | enhancer/ silencer sequences
41
Heterochromatin
highly compacted genetic material, not transcribed
42
Outline Eukaryotic elongation
RNA polymerase synthesises RNA until it reaches the termination sequence As the RNA polymerase progresses, DNA unwinds to allow the template strand to direct RNA assembly The DNA immediately returns to a helix after RNA polymerase passes by elongation follows very similar to prokaryotic transcription
43
What are 2 types of transcription termination mechanisms in bacteria?
intrinsic (more common) and rho dependent
44
Outline Eukaryotic Termination
occurs once the RNA polymerase transcribes the polyA tail, dissociating the RNA polymerase from the template DNA strand and RNase cuts the pre-MRNA strand off.
45
consensus sequence
short regions of DNA sequences that are highly similar though not necessarily identical to one another and are located in the same position relative to the start of transcription of different genes
46
rut site
a strech of approx 50 nucleotides that are rich in cysteine and poor in g
47
preinitiation complex (PIC)
in eukaryotic transcription a large multiprotein complex containing several general transcription factors and RNA polymerase 2
48
pre-mRNA
the initial transcript of a eukaryotic gene requiring mrna processing prior to translation
49
mRNA
the fully processed mRNA that comes out of the nucleus to the cytoplasm for translation
50
What are the steps to modify the pre mRNA to mature mRNA
1) 5' capping 2) Polyadenylation of the 3’ pre-mRNA 3) intron splicing
51
What must happen after termination
After transcription termination, the pre-mRNA must be modified before exportation from the nucleus
52
Addition of the 5’-cap:
protects the mRNA from degradation as its transported across the nuclear envelope and introns are spliced out Guanylyl transferase adds a guanine to the 5’ end of the pre-mRNA Produces an unusual 5’-to-5’ bond forming a triphosphate linkage Methylation of that guanine finalises the cap
53
Polyadenylation of the 3’ pre-mRNA
Cleavage and polyadenylation specificity factor (CPSF) binds to a region of AAUAAA downstream of the stop codon (therefore is non-coding) - Polyadenylation signal sequence Cleavage stimulating factor (CStF) binds to a uracil rich sequence downstream of the polyadenylation signal sequence - Other cleavage factors (CFI, CFII) and polyadenylate polymerase (PAP) also join the complex The complex cleaves 15-30 nucleotides downstream of the AAUAAA Once cut, the pre-mRNA has 20-200 adenine nucleotides added to its 3’ end to create a poly-A tail
54
what does the poly A tail function in?
Facilitating the transport of mRNA across the nuclear membrane Protecting the mRNA from degradation Enhancing translation by enabling ribosomal recognition of the mRNA
55
Splicing
removes introns and joins together the exons
56
Introns:
“intervening regions”
57
Exons:
“expressed regions”, gets translated into proteins
58
spliceosome
(protein complex that removes introns) 
59
Alternative splicing
one region that is an intron in one gene may be an exon region in depending on the protein that is to be translated
60
When does Posttranscriptional modification occurs?
Posttranscriptional modifications are coupled with transcription The 5’ cap is added after ~ 20-30 nucleotides have been transcribed
61
What are some key differences in transcription in eukrayotes and prokaryotes?
``` Prokaryotes No posttranscriptional modifications in prokaryotes Happens in the cytoplasm Has a terminator sequence no intron ``` Eukaryotes Yes posttranscriptional modifications in eukaryotes Happens in the nucleus No terminator sequence

Genetics (12 decks)

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