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Molecules and Energetics Block 1 > Translation & Genetic Code > Flashcards

Translation & Genetic Code Flashcards

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1
Q

What are the two subunits for the prokaryotic ribosome?

A

50 S +30 S=70S

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2
Q

What are the components of the prokaryotic 50S ribosome?

A

23 S and 5S (34 proteins)

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3
Q

What are the components of the 30 S prokaryotic ribosome?

A

16S rNA (21 proteins)

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4
Q

What are the two subunits for the eukaryotic ribosome?

A

60S+ 40S= 80S

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5
Q

What are the components of the 60S E. ribosome?

A

28S, 5.8 S and 5S (50 proteins)

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6
Q

What are the components of the 40S E. ribosome?

A

18S (33 proteins)

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7
Q

What is the enzyme activity of rRNA called?

A

peptidyl transferase

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8
Q

What does peptidyl transferase do?

A

Catalyzes peptide bond formation in protein synthesis

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9
Q

Where is the Shine-Dalgarno sequence?

A

Located upstream of AUG start codon in prokaryotic mRNA

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10
Q

Why do prokaryotes have multiple start/stop codons in their mRNA?

A

Polycistronic

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11
Q

What is the start codon?

A

AUG

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12
Q

What are the stop codons?

A

UAA, UGA, and UAG

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13
Q

Where is the start codon located in eukaryotic mRNA?

A

Kozak sequence

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14
Q

What are the 2 key structural components of tRNA?

A

1) Anticodon stem/loop

2) Acceptor Stem CCA-3’

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15
Q

What is the function of the anticodon stem/loop?

A

Translates genetic code of mRNA

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16
Q

What is the function of the acceptor stem?

A

“charging” of CCA-3’ terminus by aminoacyl linkage to amino acid

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17
Q

What is the sequence that is located on the 3’ end of tRNA?

A

CCA

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18
Q

What is the function of Aminoacyl-tRNA synthetases?

A

Implementation of genetic code by attaching a given AA to its correct tRNA molecule

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19
Q

How many aminoacyl-tRNA synthetases are expressed for each of the 20 AA?

A

At least one

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20
Q

Aminoacyl-tRNA synthetases must recognize these 2 things:

A

1) Cognate tRNA

2) Correct AA

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21
Q

Does aminoacyl-tRNA synthetases have low or high fidelity?

A

High fidelity b/c

1) recognizes correct AA in the active site before aminoacyl linkage with RNA is catalyzed
2) Incorrect aminoacyl linkages are removed by editing function

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22
Q

What are the 2 steps in the aminoacyl-tRNA synthetase reaction?

A

1) AA activation by formation of an Aminoacyl-AMP intermediate.
2) Charging of tRNA by transfer of AA to acceptor to form aminoacyl-tRNA

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23
Q

How many codons do we have?

A

64 triplet codons (4^3=64)

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24
Q

What is degeneracy of the genetic code?

A

More than 1 codon can be used for the same AA

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25
Q

In mRNA, how are codons read?

A

5’ to 3’

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26
Q

In tRNA, how are anticodons read?

A

3’ to 5’

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27
Q

What is “wobbling?”

A

Third base of codon exhibits uncommon base pairings with the first base of the anticodon, allowing degeneracy of the code.

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28
Q

If the anticodon 1st base is C, what is the codon 3rd base?

A

G

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29
Q

If the anticodon 1st base is A, what is the codon 3rd base?

A

U

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30
Q

If the anticodon 1st base is U, what is the codon 3rd base?

A

A or G

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31
Q

If the anticodon 1st base is G, what is the codon 3rd base?

A

U or C

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32
Q

If the anticodon 1st base is I, what is the codon 3rd base called?

A

U, C, or A

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33
Q

What is inosine?

A

deaminated adenine

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34
Q

Why is inosine special?

A

Inosine maximizes the number of codons that a tRNA molecule can read by forming non-standard base pairings

35
Q

What are the 3 steps of translation?

A

Initiation, Elongation, Termination

36
Q

What is the step of translation that differs most between P & E?

A

Initiation Step

37
Q

In prokaryotes, is the mRNA processed or spliced?

A

NO

38
Q

In prokaryotes, does transcription and translation occur simultaneously?

A

YES

39
Q

In eukaryotes, does transcription and translation occur simultaneously?

A

NO

40
Q

Where does translation occur in both prokaryotes and eukaryotes?

A

Cytoplasm

41
Q

Where does transcription occur in P?

A

Cytoplasm

42
Q

Where does transcription occur in E?

A

Nucleus

43
Q

Do prokaryotes or eukaryotes have formylated methionine?

A

Prokaryotes

44
Q

What is the main function of the Shine -Dalgarno sequence?

A

Marker that enables 30S ribosome to recognize the AUG start codon of mRNA by complementary base pairing with 16S rRNA

45
Q

What are the 2 main complexes that form in eukaryotic translation initiation?

A

Ternary Complex and the Pre-Initiation Complex

46
Q

How does the pre-initiation complex recognize the start codon?

A

via Linear Scanning 5’ to 3’ along the 5’ UTR of mRNA

47
Q

What is the role of 4E (a subunit of elF-4F)?

A

Binds to the m7Gppp cap on mRNA

48
Q

What is the role of 4G (a subunit of elF-4F)?

A

Binds to elF-3

49
Q

What is the role of 4A (a subunit of elF-4F)?

A

RNA helicase

50
Q

In prokaryotes, what initially binds to the 30S ribosomal subunit?

A

IF-1 and IF-3

51
Q

In P, what IF is bound to GTP?

A

IF-2

52
Q

What forms the ternary complex in E?

A

1) met-tRNA

2) elF-2+GTP

53
Q

What forms the initiation complex in E?

A

1) Ternary complex
2) Other ELFs
3) 40S

54
Q

Where does the pre-initation complex initially bind?

A

5’-cap

55
Q

Right before the 60S ribosome binds, what EIF binds?

A

eLF-5

56
Q

Is translation in eukaryotes separated in time and space?

A

Yes

57
Q

What are the 3 tRNA binding sites in the ribosome?

A

A site: Aminoacyl Site
P site: Peptidyl Site
E site: Exit Site

58
Q

What enzyme catalyzes peptide bond formation?

A

Peptidyl Transferases

59
Q

For prokaryotes, where is the catalytic activity of peptidyl transferase derived from?

A

23S rRNA

60
Q

For E, where is the catalytic activity of peptidyl transferase derived from?

A

28 rRNA

61
Q

Peptidyl transferases shift the nascent peptide from what site to another?

A

P site to A site

62
Q

Where is the energy for peptide bond formation derived from?

A

ATP used in tRNA charging

63
Q

To start elongation, where is the f-met/met positioned?

A

P site

64
Q

In elongation, the hydrolysis of GTP is dependent on what?

A

On the correct codon:anticodon base pairing in the A site: functions as a proof-reading mechanism

65
Q

What site does the uncharged tRNA translocate to?

A

E site

66
Q

Binding of the next AA-tRNA to the A site causes the release of what?

A

Uncharged tRNA from the E site

67
Q

What is EF-Tu?

A

1) Proka. Elong Factor

2) Recruits AA-tRNA to A site; GTP hydrolysis

68
Q

What is eEF-1α?

A

1) Eukaryotic. Elong Factor

2) Recruits AA-tRNA to A site; GTP hydrolysis

69
Q

What is EF-Ts?

A

1) Prok Elong Factor
2) Exchange GDP-Pi for GTP
3) Exchange activates EF-Tu

70
Q

What is eEF-1βY?

A

1) Euk Elong Factor
2) Exchange GDP-Pi for GTP
3) Exchange activates EF-Tu

71
Q

What is EF-G?

A

1) prok Elong factor

2) Translocation of Peptidyl tRNA; GTP-hydrolysis

72
Q

In elongation, how is the mRNA template read?

A

Coding sequence is read in the 5’ to 3’ direction

73
Q

In elongation, what is the direction of polypeptide synthesis?

A

Polypeptide grows from amino end to carboxy end

74
Q

What are multiple ribosomes translating a single mRNA molecule to improve efficiency?

A

Polysomes

75
Q

What is translational efficiency?

A

of ribosomes/ mRNA molecule

76
Q

What is the role of protein chaperones?

A
  1. Chaperones function co-translationally

2. Facilitate proper protein folding

77
Q

The correct 3-D conformation of protein is determined by?

A

AA sequence

78
Q

In termination, what site does the stop codon go?

A

A site

79
Q

What proteins recognize the stop codon and bind to the A site?

A

Release Factors (RF)

80
Q

Binding of RFS to the A site stimulates what?

A

Hydrolysis of the bond btw the C-terminal AA of polypeptide chain and tRNA in the P site

81
Q

Streptomycin does what?

A

Inhibits formation of 70S initation complexes targets 30 S

82
Q

Tetracycline does what?

A

Targets 30 S by inhibiting binding of aminoacyl-tRNAs to the A site

83
Q

Chloramphenicol does what?

A

Targets 50 S subunit; inhibits peptidyl transferase reaction to block formation of peptide bonds

84
Q

What does erythromycin do?

A

Targets 50 S subunit: inhibits translocation of peptidyl-tRNA from the A site to the P site

Molecules and Energetics Block 1 (4 decks)

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