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Molecular Biology > Final Exam > Flashcards

Final Exam Flashcards

1
Q

what part of an mrna sequence helps e.coli distinguish the start codon from a methionine codon

A

shine delgarno sequence (towards the 5’ end of AUG)

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2
Q

what modification helps e.coli distinguish between an initiator trna and a regular trna

A

fMet

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3
Q

what does IF3 do

A

inhibits premature formation of 70S ribosome

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4
Q

what does EF-Tu do

A

delivers aminoscyl-trna to the A site

binds GTP/GDp

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5
Q

what does the 50S subunit do

A

forms the peptide bond

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6
Q

what does IF2 do

A

delivers fMet-tRNA to the P site

binds GTP/GDP

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7
Q

what does eIF4f do

A

initiates cap dependent translation

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8
Q

what does EF-G do

A

binds GTP/GDP

promotes translocation of the ribosome

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9
Q

what proteins/complexes hydrolyze GTP during translation

A

EF-Tu, RF3, IF2, EF-G

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10
Q

what functional change must be made to Cas9 to be used for CRISPRi or CRISPRa

A

mutate so it wont cut (dCAS9)

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11
Q

how can you modify the cas9 system in order to inhibit gene expression without modifying the DNA sequence

A

fuse a protein domain that will prevent binding of RNA pol III
dCAS9 will target specific region, inhibitor domain will prevent transcription, reducing gene expression

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12
Q

T or F: the 30S ribosome associates with the mrna before the 50S

A

true

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13
Q

T or F: N-formylmethionyl-trna^fmet binds in the p site

A

true

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14
Q

T or F: EF-Tu-GTP binds to the 50S ribosome

A

false

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15
Q

T or F: IF-1, IF-2, IF-3 dissociate before the 50S subunit binding

A

true

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16
Q

describe the wobble hypothesis

A

the variance in base pairing is greater at the 5’ end of the anticodon, thus accounting for more than one codon
non WC base pairing is sometimes allowed in the last position of the codon
G and U can pair as well

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17
Q

are trna molecules ds or ss

A

single stranded RNA

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18
Q

which terminal of the trna is the site of AA attachment

A

3’ terminal

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19
Q

T or F: the anticodon arm of trna contains a three nucleotide sequence that is identical to a specific mrna codon

A

false

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20
Q

can a single trna bind to multiple mrna codons?

A

yes

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21
Q

where does the energy to create a peptide bond in the peptidyl transferase reaction come from

A

energy is stored in ester bond, positioned by EF-Tu and peptidyl transferase

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22
Q

is a promoter region found within the mrna transcript

A

no

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23
Q

is a kozak sequence found within the mrna transcript

A

yes

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24
Q

is a stop codon found within the mrna transcript

A

yes

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25
Q

is a shine delgarno sequence found within a mrna transcript

A

yes

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26
Q

what is the sequence of mRNA for a polypeptide that encodes 4 Met residues

A

AUG AUG AUG AUG

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27
Q

what is the coding strand of DNA for the peptide 5’ AUG AUG AUG 3’

A

5’ ATG ATG ATG ATG 3’

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28
Q

what is the template strand of DNA for the polypeptide 5’ AUG AUG AUG AUG 3’

A

3’ TAC TAC TAC TAC 5’

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29
Q

what is the Met tRNA anticodon

A

5’ CAU 3’

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30
Q

what part of the mRNA sequence help E. coli distinguish the start codon from other met codons

A

shine-delgarno sequence (towards 5’ end of AUG)

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31
Q

what modification helps E. coli distinguish between an initiator tRNA and a regular tRNA

A

fMET

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32
Q

describe the wobble hypothesis

A

variance in base pairing is greater at 5’ end of anticodon, accounting for more than one codon
non W-C base pairing can be allowed in last position of the codon

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33
Q

imagine a mutation that makes gln aminoacyl synthetase recognize and bind to the tRNA^asn
would this mutation change the mRNA sequence

A

no

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34
Q

guanine nucleotide exchange factors are a set of proteins that activate GTPases by exchanging a GDP for a GTP
imagine a new eukaryotic protein that phosphorylated to a site on eIF2 that prevented eIF2 from binding its guanine nucleotide exchange factor
what would happen to the number of tRNAi^met

A

the number of charged initiator met would increase since they are not being used to start new protein synthesis; number of uncharged tRNAi^met would decrease

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35
Q

guanine nucleotide exchange factors are a set of proteins that activate GTPases by exchanging a GDP for a GTP
imagine a new eukaryotic protein that phosphorylated to a site on eIF2 that prevented eIF2 from binding its guanine nucleotide exchange factor
what would happen to the levels of protein translation

A

protein translation would decrease since they cant initiate new proteins

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36
Q

mRNA: 5’ ACC GCC AUG CAU CAC CAC CAU 3’

what is the coding strand of DNA

A

5’ ACC GCC ATG CAT CAC CAC CAT 3’

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37
Q

mRNA: 5’ ACC GCC AUG CAU CAC CAC CAU 3’

what is the AA sequence translated by the ribosome

A

met-his-his-his-his

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38
Q

mRNA: 5’ ACC GCC AUG CAU CAC CAC CAU 3’

what is the AA sequence once the peptide sequence has been processed into a functional protein

A

His His His His

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39
Q

mRNA: 5’ ACC GCC AUG CAU CAC CAC CAU 3’

what are the anticodons used to translate this mRNA

A 
5' ---> 3'
CAU (met)
GUG (his)
GUG (his)
GUG (his)
GUG (his)
40
Q

insertions or deletions of one or two DNA nucleotides can cause what kind of mutations

A

frameshift mutations

41
Q

where is the anticodon on the tRNA

A

bottom of the “t”

42
Q

which end of the tRNA does the specific amino acid bind to

A

the 3’ end

43
Q

T or F: the aminoacyl synthetase uses base pairing in the anticodon region to determine tRNA identity

A

false

44
Q

what is aminoacyl synthetase

A

enzyme that attaches the right amino acid onto the tRNA

45
Q

how does aminoacyl synthetase determine tRNA identity

A

the overall configuration of the tRNA

46
Q

what is the role of IF1

A

prevents premature binding of the incoming tRNA to the A site

47
Q

what is the role of IF2

A

loads in the fMET (initiator) tRNA into the 30s subunit

48
Q

what is the role of IF3

A

prevents premature binding of the 50s subunit

49
Q

what is the role of fMET

A

initiator tRNA that binds to the start codon

50
Q

what is the role of the sine delgarno sequence

A

binds to the 16s rRNA to position start codon in the P-site

51
Q

in EUKARYOTIC transcription initiation

what are the two roles of eIF4F in translation

A

bind mRNA and load it into small subunit

induce mRNA circularization

52
Q

in EUKARYOTIC transcription initiation

which protein binds and then loads the initiator tRNA into the small subunit

A

eIF2

53
Q

T or F: the initiator tRNA is loaded into the small subunit before the mRNA

A

true

54
Q

if the genome annotation only used the AUG start codon to identify ORFs, but the leaderless start codon does not need to be AUG, what is suggested about the potential proteins in bacterium

A

there could be other proteins that do not use the AUG start codon that would not be recognized by the genome annotation algorithm

55
Q

what are the two non-canonical mechanisms that give rise to the wobble hypothesis

A

U can basepair with G and A

I can basebair with C,U,A

56
Q

in a BACTERIAL ribosome

what are the sizes of the subunits

A

large subunit: 50s

small subinit: 30s

57
Q

in a BACTERIAL ribosome

which way does the mRNA run from L to R

A

5’ –> 3’

58
Q

in a BACTERIAL ribosome

what order do the ribosomal tRNA sites go from L—>R

A

EPA

59
Q

considering BACTERIAL translation initiation

T or F: EF-Tu-GTP bind to the 50s ribosome

A

false

60
Q

considering BACTERIAL translation initiation

T or F: the 30s ribosome associated with the mRNA before the 50s ribosome

A

true

61
Q

considering BACTERIAL translation initiation

T or F: IF-1, IF-2, IF-3 dissociate before the 50s subunit binding

A

true

62
Q

considering BACTERIAL translation initiation

T or F: N-formylmethionyl-tRNS^fmet binds in the p site

A

true

63
Q

consider the aspartic acid (asp) aminoacyl synthetase

what is the first step required to charge the tRNA

A

adenylating the AA (linking the free AA with an ATP)

64
Q

consider the aspartic acid (asp) aminoacyl synthetase

what is the notation of the tRNA upon charging with the right AA

A

asp-tRNA^asp

65
Q

consider the aspartic acid (asp) aminoacyl synthetase
imagine a mutation in the asp tRNA such that it is only recognized by the glu synthetase. what is the notation of the tRNA in this mutated charged context

A

glu-tRNA^asp

66
Q

consider the synthetitc protein GCaMP (Ca binding domain) sensor
given that this protein is synthetic, why can it work inside cells

A

protein function is modular so the pieces can still do their roles when fused together in the cell

67
Q

consider the synthetitc protein GCaMP (Ca binding domain) sensor
how could you make a new synthetic protein that has a fluorescent readout that senses Ca only near the ribosome

A

fuse the GCaMP proein onto a ribosomal protein that targets only to ribosomes

68
Q

when considering ribosomal sizes, what does S stand for

A

Svedbergs

69
Q

which statements describe transcription factors

  1. binds specific sequence of DNA
  2. binds only at promoter regions
  3. changes affinity for RNA pol
  4. changer affinity for DNA pol
  5. is correctly positioned on DNA by anticodon base-pairing
A
  1. and 3. are correct
70
Q

which statements correctly describe co-activators

  1. binds specific sequence of DNA
  2. binds only at promoter regions
  3. changes affinity for RNA pol
  4. changes affinity for DNA pol
  5. is correctly positioned on the DNA by anticodon basepairing
A
  1. is correct
71
Q

what type of protein secondary structure in transcription factors can read out the identity of nucleotides

A

alpha-helix

72
Q

which region of the base (A,T,G,C) is used by transcription factors to chemically distinguish the identity of the nucleotides

A

major groove

73
Q

T or F: LacI disrupts W-C basepairing when binding to the operator

A

false

74
Q

what is the signal recognition particle

A

cytoplasmic protein complex

75
Q

what is the function of the signal recognition particle

A

bind the N-terminal end of growing polypeptides for membrane translocation

76
Q

imagine a mutation in the lac operator such that lacI is unable to bind
which of the following would occur
1. in the presence of lactose, no mRNA would be produced
2. in the presence of lactose, some mRNA would be produced
3. in the absence of lactose, no mRNA would be produced
4. in the absence of lactose, some mRNA would be produced

A
  1. and 4. are correct
77
Q

a mutation in a eukaryotic gene induces an extra 80 AA in the translated product
what type of mRNA likely occurred

A

non-stop mRNA

78
Q

a mutation in a eukaryotic gene induces an extra 80 AA in the translated product
what is the most likely identity of the last AA

A

lysine

79
Q

imagine a mutation in BACTERIA such that the ribosome reaches the end of the mRNA without recruiting RF1 or RF2
what is the name of the structural mimic that can rescue this type of mutation

A

tmRNA

80
Q

imagine a mutation in BACTERIA such that the ribosome reaches the end of the mRNA without recruiting RF1 or RF2
briefly describe how the structural mimic tmRNA is able to salvage the ribosome

A

the tRNA mimic portion loads into the A-site and catalyzes the peptide transfer to an alanine. the other mRNA like pieces of the tmRNA are then read by charged tRNAs as per usual

81
Q

T or F: enhancers only increase transcriptional activity of genes that are located thousands of basepairs away in the genome

A

false

82
Q

imagine a mutation in the bacterial L4 protein involved in regulation of ribosomal protein production. this mutation renders the L4 protein unable to bind to the mRNA
what would occur??

A

the amount of ribosomal proteins would increase

83
Q

of the 7 points of regulation of protein expression, which is most heavily regulated by the cell

A

transcription initiation

84
Q

why is transcription initiation most heavily regulated by the cell

A

so that no energy is wasted downstream in mRNA or protein production

85
Q

what are 4 different mechanisms that are used by cells to alter protein activity post-translationally

A

phosphorylation, dimerization, translocation, ubiquitination

86
Q

cystic fibrosis is caused by defects in the CFTR protein (uses ATP to move Cl ions across plasma membrane) and if it doesnt work fluid builds up, resulting in disease.
how could a mutation in the first 20 AA induce disease if it does not affect Cl pumping ability

A

the mutation could prevent trafficking to the plasma membrane

87
Q

which of the following statements are true

  1. every cell in the human body has the same DNA sequence
  2. every cell in the human body has the same histone mark patterns
  3. every cell in the human body transcribed the same mRNAs
  4. every cell in the human body translates the same proteins
A
  1. is true
88
Q

imagine a mutation in yeast that prevents binding of Gal4p from the gal promoter sequence
how would this mutation affect the expression of the GAL genes

A

they would never be expressed because the activator could never recruit the RNA polymerase to that location

89
Q

how would a mutation that prevents expression of recA affect the expression of the SOS genes in E. coli

A

it would prevent SOS gene expression in the presence of widespread damage

90
Q

what are all the possible codons for Phe

A

5’ UUU 3’

5’ UUC 3’

91
Q

what are all the possible anticodons for Phe

A

5’ AAA 3’

5’ GAA 3’

92
Q

for an organism that only has one tRNA for Phe, what would the anticodon likely be

A

5’ GAA 3’

93
Q

what modification on which AA helps E. coli distinguish between an initiator tRNA and a regular tRNA

A

formyl group on methionine

94
Q

design a forward primer for the ORF with 6 nucleotides and a PstI cutsite
DNA sequence:
5’ CAACCTAATGCACCCCGATTCCATAAAGTAAAACCTTCAACTC 3’

A

5’ CTGCAG ATG CAC 3’

95
Q

design a reverse primer for the ORF with 6 nucleotides and a EcoRV cutsite
DNA sequence:
5’ CAACCTAATGCACCCCGATTCCATAAAGTAAAACCTTCAACTC 3’

A

3’ AAG TAA GATATC 3’

(want in 5’ –> 3’ direction)

5’ GATATC TTA CTT 3’

Molecular Biology (4 decks)

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