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Theme 2B Flashcards

Transcriptional and Post-Transcriptional Gene Regulation (69 cards)

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1
Q

Transcriptional regulation of gene expression

A
  1. Initiation
  2. Elongation
  3. Termination
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2
Q

Differential expression of genome

A
  • when not all genes are being turned on
  • gives rise to different cell types and tissues
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3
Q

Organism’s phenotype is dependant on

A

cell number, type, and function

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4
Q

Every cell in an organism has an ____________

A

identical genome (DNA sequence)

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5
Q

Turning on a gene means going from ______ to __________________________

A

DNA; transcription

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6
Q

Structure and function of a gene

A

gene includes a promoter and transcriptional unit

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7
Q

Promoter

A

DNA sequence (includes TATA box) that specifies where transcription begins on chromosome

  • signal or landing spot for enzymes so location of specific gene can be identified
  • located immediately upstream or 5’ of the transcriptional starting point of the non-template or coding DNA strand
  • bound and recognized by transcriptional machinery
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8
Q

Transcriptional machinery

A

initiate transcription

  • RNA polymerase and transcription factors
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9
Q

Transcriptional unit

A

part of the gene that is copied into RNA

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10
Q

RNA polymerase: enzymes of transcription

A

synthesize RNA transcript in a 5’-3’ direction while reading DNA template in the 3’-5’ direction

  • does not need primer for initiation of RNA synthesis
  • unwinds and rewinds DNA helix during RNA synthesis
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11
Q

3 types of RNA polymerase

A

RNA polymerase I

RNA polymerase II

RNA polymerase III

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12
Q

RNA pol I

A

transcribes rRNA

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13
Q

RNA pol II

A

transcribes mRNA

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14
Q

RNA poly III

A

transcribes tRNA

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15
Q

Step 1: Transcriptional Initiation

A

transcriptional initiation is mediated by direct interaction of DNA-binding proteins to specific regulatory sequences of the gene (rate determining step)

2 types of processes:
- general transcriptional factors bind to promoter and recruite RNA poly II resulting in LOW BASAL LEVEL of transcription (gene expression = low)

  • transcriptional activator proteins bind to enhancer regions distant from promoter to cause DNA looping bringing mediator and RNA polymerase to promoter resulting in HIGH LEVEL of transcription
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16
Q

Step 2: Transcriptional Elongation

A

RNA pol moves along template DNA (3’ to 5’)

DNA is unwound in front of moving RNA poly and reannealed behind in the transcription bubble

Ribonucleotides are added to the 3’ end of the RNA transcription (synthesis continues 5’-3’)

growing RNA transcript is displaced from DNA template strand to allow reannealing back into double stranded DNA

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17
Q

Step 3: Transcriptional Termination

A

5- sequence in DNA template causes termination after transcribed into RNA

  1. Rho-independant termination
  2. Rho-dependant termination
  3. Cleavage & polyadenylation specifc factor
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18
Q
  1. Rho-independant termination
A

prokaryotes

terminator sequence in mRNA base pairs with itself to form G-C hairpin and causes RNA polymerase to stall and dissociate

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19
Q
  1. Rho-dependant termination
A

prokaryotes

terminator sequence in mRNA is recognized and bound by the Rho helicase which unwinds the RNA from template DNA and RNA polymerase

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20
Q
  1. Cleavage & polyadenylation specific factor
A

eukaryotes

poly-A sequence in mRNA signals the CPSF to cleave the completed mRNA transcript thereby separating it from RNA polymerase

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21
Q

When is the RNA molecule the longest during transcription

A

end of transcription as it reads more

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22
Q

When is the RNA molecule the shortest during transcription

A

start of transcription as it reads more as you go

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23
Q

In transcription, RNA molecules are _____________

single/double strands?

A

single strands

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24
Q

transcription occurs at _______ in the genome

A

selected locations

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25
In transcription, synthesis of RNA occurs in __________ and copies vary throughout genome
multiple copies
26
In transcription, RNA poly does not need a _________ for initiation
primer
27
In transcription, RNA product does not remain ________ to the template DNA
base-paired
28
In transcription, synthesis of RNA occurs in the _________ direction
5'-3'
29
In DNA replication, DNA molecules are | single/double stranded?
double stranded
30
In DNA replication, replication occurs for the ___________
entire genome
31
In DNA replication, genome is only replicated _____________
once/cell cycle
32
In DNA replication, DNA poly requires __________ for initiation
primer
33
In DNA replication, daughter strand remains ____________ with parental template strand
base-paired
34
In DNA replication, synthesis of new DNA strand occurs in the ______ direction
5'-3'
35
Posttranscriptional regulation of gene expression has 3 steps:
1. 5' capping 2. 3' polyadenylation 3. splicing
36
The ends of prokaryotic and eukaryotic mRNAs are __________
not translated
37
Both 5'-UTRs and 3'-UTRs regulate
mRNA stability and translational efficiency
38
5'-UTRs contain
ribosome binding stie (RBS) or Shine Dalgarno sequence in prokaryotes & Kozak box sequences in eukaryotes that function in translational initiation
39
Open reading frame (ORF)
region of mRNA that is translated and includes the start and stop codons at the borders
40
The newly transcribed mRNA (pre-mRNA) undergoes processing in the ________ to produce ___________
nucleus ; mature translatable mRNA
41
1. 5'CAP
modified guanosine triphosphate is added to the 5' end of the mRNA and acts as a ribosome binding site (attracts r to 5') and protects mRNA from degradation
42
Poly(A) tail
long string of adenine nucleotides added to the 3' end of the mRNA by poly-A polymerase to protect the mRNA from being degraded & increase translational efficiency
43
Introns are removed/spliced during ___________ to ____________b/c
pre-mRNA processing; produce translatable mRNA because they don't contain codon
44
If you remove poly (A), what enzyme degrades?
5'-3' exoribonuclease
45
The longer the poly-A, the more
stable
46
Posttranscriptional processing from pre-mRNA to mRNA
newly-transcribed precursor mRNA (pre-mRNA) needs to be converted to a translatable mRNA because it cannot be yet translated into a protein - addition of 5'-CAP and poly-A tail - pre-mRNA has a mix of alternating coding segments and UTRs (exons) and non-coding segments (introns) - removal of introns by splicing to generate the open reading frame consisting of a continuous stretch of codons & URTs - mRNA is exported from nucleus into the cytoplasm to associate with ribosomes
47
Why is removal of introns by splicing important?
if they are not removed, you won't get functional protein
48
Exons
coding segments and UTR
49
Introns
non-coding segments
50
mRNA splicing
removal of introns from pre-mRNA and joining of exons to make mature mRNA
51
spliceosome
- carries out splicing - made out of snRNA and splicing proteins - made up of five non-coding RNAs (snRNA) complexed to several proteins (small ribonucleoprotein particles/ snRNPs)
52
Process of Splicing in 4 steps
1. Spliceosome binds to intron-exon junctions 2. Loops introns out of the pre-mRNA (lariat structure) bringing exons closer together 3. Clip the intron at each exon boundary releasing the lariat structure 4. Join adjacent exons together
53
Alternative splicing
splicing can occur in different combinations to generate two or more different mRNAs from a gene, and several related protein products (isoforms) - different isoforms are made in diff tissues from the same gene, producing tissue-specific phenotypes - increases the number and variety of proteins that can be encoded by a genome
54
Posttranscriptional regulation by RNA interference
found in all eukaryotes microRNA transcribed by RNA Pol II; small interfering RNA also transcribed (siRNAs) - miRNA/siRNA precursors are cleaved to 21-23 bp double-stranded RNAs by the Dicer Rnase - these double stranded RNAs are substrates of RISC - likely evolved as an antiviral mechan9ism to destroy viral mRNA
55
RISC
RNA induced-silencing complex - unwinds one of the RNA strands which attracts binding of complementary mRNA
56
(Posttranscriptional regulation by RNA interference) Binding of the mRNA to RISC interferes with ____________ or induces ___________
translation initiation; mRNA degradation (represses gene expression)
57
Transcriptional regulation
control of mRNA synthesisT
58
Transcription rate depends on the
speed of transcriptional initiation (promoter strength)
59
Posttranscriptional regulation
processing of mRNA which affect- usually improves - its stability & translational efficiency
60
Stability of mRNA depends on the presence of ____________ & _______________
5'-CAP & length of poly-A tail
61
Expression level of a specific gene depends on the ___________, ____________, and it's eventual _______
abundance of mRNA, nucleotide sequence, eventual translation
62
Abundance of RNA depends on
rate of synthesis (transcription) and degradation of mRNA (posttranscriptional)
63
More RNA = More
Protein - depends on RNA stability
64
If the enhancer is deleted... Level of gene regulation affected= Gene expression increases/decreases Molecular process affected =
- transcription - decreases - RNA polymerase cannot initiate transcription (gene expression decreases)
65
If polyadenylation of mRNA is increased... Level of gene regulation = Gene expression increases/decreases Molecular process affected =
- post-transcription - increased - enhanced mRNA stability & translation
66
If 5'-CAP is removed... Level of gene regulation = Gene expression increases/decreases Molecular process affected =
- post-transcription - decreases - mRNA degradation accelerated, less efficiency in translation initiation
67
If TATA box is deleted.... Level of gene regulation = Gene expression increases/decreases Molecular process affected =
- transcription - decreases - formation of transcriptional initiation complex is hindered
68
If siRNA synthesis is inhibited.... Level of gene regulation = Gene expression increases/decreases Molecular process affected =
- post-transcription - increases - less mRNA degradation
69
Review slide 20

BIOL243 (7 decks)

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