BIO226 > Topic 5 > Flashcards

Topic 5 Flashcards

(51 cards)

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1
Q

What are the enzymes found in RNA viruses that can be used to replicate RNA?

A

RNA dependent RNA polymerase

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2
Q

What is an example to the rule that proteins cannot replicate themselves?

A

prions-can convert normal proteins into misfolded proteins

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3
Q

What are the two main differences between prokaryotic and eukaryotic transcription and translation?

A

Pro-coupled together, both occur in cytoplasm
Euk-different compartments, mRNA doesn’t have to be used for translation right away

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4
Q

What is catalytic RNA called?

A

ribozyme

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5
Q

Where is the OH group in RNA?

A

position 2

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6
Q

What are snRNAs?

A

structural components of the splicesosomes

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7
Q

What are miRNAs?

A

short, single stranded RNAs that block expression of complementary RNAs

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8
Q

In what direction is RNA synthesized?

A

5’-3’

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9
Q

What strands of the DNA is RNA complementary and identical to, respectively?

A

complementary-antisense
identical-sense

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10
Q

Why is RNA synthesis required to go in the direction that it does?

A

RNA pol can only catalyze the phosphodiester bond by bringing the phosphate of free nucleotides to the hydroxyl of the RNA strand attached to the DNA template

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11
Q

What are some examples of genes that are continuously transcribed?

A

housekeeping genes-rRNA

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12
Q

What are the three stages of transcription in prokaryotes?

A
  1. RNA chain initiation
  2. RNA chain elongation
  3. RNA chain termination
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13
Q

What is the o subunit responsible for in RNA pol

A

initiation of transcription

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14
Q

What is the function on the a subunit in the RNA pol

A

assembly of tetrameric core

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15
Q

What is the function of the B unit in RNA pol?

A

ribonucleoside triphosphate binding site

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16
Q

What is the function of the B’ subunit in RNA pol

A

DNA template binding region?

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17
Q

What is the function of the w subunit in RNA pol?

A

chaperon-correct folding on B’

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18
Q

What initiates transcription in prokaryotes?

A

o subunit associates with holoenzyme and binds to promoter

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19
Q

True or false: one o subunit can bind all promoters.

A

False

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20
Q

What unwinds the DNA?

A

RNA pol

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21
Q

Where does transcription (aka bps added) truly start?

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A

between promoter and ATG - aka 5’UTR

22
Q

True or false: DNA rewinding requires energy after transcription

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A

False-just h bonds reformed

23
Q

What are the two ways transcription can be terminated in bacteria?

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A

factor dependent or intrinsic termination

24
Q

What are the four steps of Rho dependent termination?

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A
  1. pause at TS
  2. p binds rut sequence
  3. RNApol/RNA displacement from template
  4. RNA release
25
How does intrinsic termination work?
stretch of GCs before As in DNA form a hairpin structure and weakens association with DNA template
26
How many RNA pols do animals and plants have, respectively?
Animals-3 Plants-5
27
What is the purpose of having multiple RNA pol?
specialize in subsets of gene templates
28
What RNA pol IIs main role?
transcribes mRNA
29
What is needed for eukaryotic cells for transcription initiation?
transcription factors to guide RNA pol to sequences
30
What is the TATA box?
common promoter sequence in eukaryotes 30bp upstream from start site
31
What are the four steps of transcription initiation in eukaryotes?
1. TFIID binds promoter at TATA box 2. PIC formed with association of TFIIH, TFIII and TFIF which brings pol to site 3. TFIIF, D and I leave which allows for elongation 4. coupled with phosphorylation of fRNA pol at C terminal domain
32
How does the C terminus domain play such a critical role in RNA processing?
phosphorylation of certain CTDs changes RNA pols affinity to different processing factors (i.e. capping, splicing etc.)
33
What is the 5' cap?
unusual 5'-5' phosphodiester bond between a methylated guanine nucleotide to the first transcribed nucleotide in the RNA
34
What is the purpose of a 5' cap?
1. transport across nuclear envelope 2. protection from nucleases 3. recognition signal
35
What is the end of transcription signal and what occurs?
end of transcription signal-polymerase stalls and endonuclease cleaves downstream of an AU rich region
36
What recognizes the cleaved transcript?
Poly A polyermase
37
What is the purpose of the PABP?
stabilize transcript and protects from degradation
38
What is the purpose of a poly A tail?
enhances mRNA stability in cytoplasm and promotes translation
39
What is the mature mRNA that is exported into the cytoplasm?
coding sequences with 5' cap and 3' tail
40
Why is splicing important?
increases protein diversity (i.e. 3 exons, only two used, different proteun)
41
What is an R loop?
non template DNA strands looping around thick RNA-DNA heteroduplexes
42
What do the boundaries of an R loop tell us?
interval of an exon
43
How did R loops let us know there were introns?
mouse beta globin showed more than one R loop
44
What is an example of splicing leading to a harmful mutation?
tub gene leading to obesity
45
What are the conserved sequences for splicing?
dinucleotide sequences at 5' and 3' branch point adenine TACTAAC box around 30 nt upstream from 3' splice site
46
What are the two consecutive reactions needed for splicing?
transesterfications
47
What is involved in the first transesterification?
P of last nt in upstream exon and oh of branch site adenine
48
What is involved in the second transesterification?
free 3'OH of cleaved upstream exon and P of first P of nt of downstream exon
49
What are the two main mechanisms of splicing?
1. self-ribozyme 2. spliceosome
50
What is the spliceosome?
RNA and protein structure in the nucleolus-form SNRPs
51
What is the main difference between self splicing and spliceosome?
use of guanosine as cofactor and thus no lariat formed
BIO226
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