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

Translation & Genetic Code Flashcards

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
In mRNA, how are codons read?
5' to 3'
26
In tRNA, how are anticodons read?
3' to 5'
27
What is "wobbling?"
Third base of codon exhibits uncommon base pairings with the first base of the anticodon, allowing degeneracy of the code.
28
If the anticodon 1st base is C, what is the codon 3rd base?
G
29
If the anticodon 1st base is A, what is the codon 3rd base?
U
30
If the anticodon 1st base is U, what is the codon 3rd base?
A or G
31
If the anticodon 1st base is G, what is the codon 3rd base?
U or C
32
If the anticodon 1st base is I, what is the codon 3rd base called?
U, C, or A
33
What is inosine?
deaminated adenine
34
Why is inosine special?
Inosine maximizes the number of codons that a tRNA molecule can read by forming non-standard base pairings
35
What are the 3 steps of translation?
Initiation, Elongation, Termination
36
What is the step of translation that differs most between P & E?
Initiation Step
37
In prokaryotes, is the mRNA processed or spliced?
NO
38
In prokaryotes, does transcription and translation occur simultaneously?
YES
39
In eukaryotes, does transcription and translation occur simultaneously?
NO
40
Where does translation occur in both prokaryotes and eukaryotes?
Cytoplasm
41
Where does transcription occur in P?
Cytoplasm
42
Where does transcription occur in E?
Nucleus
43
Do prokaryotes or eukaryotes have formylated methionine?
Prokaryotes
44
What is the main function of the Shine -Dalgarno sequence?
Marker that enables 30S ribosome to recognize the AUG start codon of mRNA by complementary base pairing with 16S rRNA
45
What are the 2 main complexes that form in eukaryotic translation initiation?
Ternary Complex and the Pre-Initiation Complex
46
How does the pre-initiation complex recognize the start codon?
via Linear Scanning 5' to 3' along the 5' UTR of mRNA
47
What is the role of 4E (a subunit of elF-4F)?
Binds to the m7Gppp cap on mRNA
48
What is the role of 4G (a subunit of elF-4F)?
Binds to elF-3
49
What is the role of 4A (a subunit of elF-4F)?
RNA helicase
50
In prokaryotes, what initially binds to the 30S ribosomal subunit?
IF-1 and IF-3
51
In P, what IF is bound to GTP?
IF-2
52
What forms the ternary complex in E?
1) met-tRNA | 2) elF-2+GTP
53
What forms the initiation complex in E?
1) Ternary complex 2) Other ELFs 3) 40S
54
Where does the pre-initation complex initially bind?
5'-cap
55
Right before the 60S ribosome binds, what EIF binds?
eLF-5
56
Is translation in eukaryotes separated in time and space?
Yes
57
What are the 3 tRNA binding sites in the ribosome?
A site: Aminoacyl Site P site: Peptidyl Site E site: Exit Site
58
What enzyme catalyzes peptide bond formation?
Peptidyl Transferases
59
For prokaryotes, where is the catalytic activity of peptidyl transferase derived from?
23S rRNA
60
For E, where is the catalytic activity of peptidyl transferase derived from?
28 rRNA
61
Peptidyl transferases shift the nascent peptide from what site to another?
P site to A site
62
Where is the energy for peptide bond formation derived from?
ATP used in tRNA charging
63
To start elongation, where is the f-met/met positioned?
P site
64
In elongation, the hydrolysis of GTP is dependent on what?
On the correct codon:anticodon base pairing in the A site: functions as a proof-reading mechanism
65
What site does the uncharged tRNA translocate to?
E site
66
Binding of the next AA-tRNA to the A site causes the release of what?
Uncharged tRNA from the E site
67
What is EF-Tu?
1) Proka. Elong Factor | 2) Recruits AA-tRNA to A site; GTP hydrolysis
68
What is eEF-1α?
1) Eukaryotic. Elong Factor | 2) Recruits AA-tRNA to A site; GTP hydrolysis
69
What is EF-Ts?
1) Prok Elong Factor 2) Exchange GDP-Pi for GTP 3) Exchange activates EF-Tu
70
What is eEF-1βY?
1) Euk Elong Factor 2) Exchange GDP-Pi for GTP 3) Exchange activates EF-Tu
71
What is EF-G?
1) prok Elong factor | 2) Translocation of Peptidyl tRNA; GTP-hydrolysis
72
In elongation, how is the mRNA template read?
Coding sequence is read in the 5' to 3' direction
73
In elongation, what is the direction of polypeptide synthesis?
Polypeptide grows from amino end to carboxy end
74
What are multiple ribosomes translating a single mRNA molecule to improve efficiency?
Polysomes
75
What is translational efficiency?
of ribosomes/ mRNA molecule
76
What is the role of protein chaperones?
1. Chaperones function co-translationally | 2. Facilitate proper protein folding
77
The correct 3-D conformation of protein is determined by?
AA sequence
78
In termination, what site does the stop codon go?
A site
79
What proteins recognize the stop codon and bind to the A site?
Release Factors (RF)
80
Binding of RFS to the A site stimulates what?
Hydrolysis of the bond btw the C-terminal AA of polypeptide chain and tRNA in the P site
81
Streptomycin does what?
Inhibits formation of 70S initation complexes targets 30 S
82
Tetracycline does what?
Targets 30 S by inhibiting binding of aminoacyl-tRNAs to the A site
83
Chloramphenicol does what?
Targets 50 S subunit; inhibits peptidyl transferase reaction to block formation of peptide bonds
84
What does erythromycin do?
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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