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Translation Flashcards

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1
Q

Translation

What are the 3 different RNAs needed for translation?

A

mRNA (messenger RNA)
rRNA (ribosomal RNA)
tRNA (transfer RNA)

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2
Q

Translation

What is the role of mRNA in translation?

A

Delivers messages containing gene code

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3
Q

Translation

What is the role of rRNA in translation?

A

Major component of ribosomes
Site of translation
Enzymatic activity

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4
Q

Translation

What is the role of tRNA in translation?

A

Translates mRNA code to amino acid code

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5
Q

Translation

Where do you find ribosomes in the cytoplasm?

A

Associated to the ER

Or free moving

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6
Q

Translation

What do all ribosomes consist of?

A

A small and a large subunit

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7
Q

Translation

How are ribosome subunits and rRNA classified?

A

According to size

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8
Q

Translation

What units are used to measure ribosome size?

A

Svedberg units (S)

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9
Q

Translation

What forms the scaffold part of the ribosome?

A

Ribosomal proteins

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10
Q

Translation

What is the size of a bacterial ribosome?

A

70S

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11
Q

Translation

What is the size of a eukaryotic ribosome?

A

80S

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12
Q

Translation

What is the principle of the Svedberg unit?

A

S = the speed a particle will travel (um/s) under an acceleration of a million gravities
A larger particle will have a large S value

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13
Q

Translation

What is weird about the S value of the whole ribosome when compared to it’s subunits?

A

The subunits S value doesn’t add together to equal that of the whole

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14
Q

Translation

Are ribosomes conserved?

A

Very much so

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15
Q

Translation

What are the sizes of the subunits in prokaryotic ribosomes?

A

Large subunit = 50S

Small subunit = 30S

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16
Q

Translation

What makes up the small subunit in prokaryotic ribosomes?

A

16S rRNA

21 proteins

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17
Q

Translation

What makes up the large subunit in prokaryotic ribosomes?

A

23S rRNA
5S rRNA
34 proteins

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18
Q

Translation

What are the sizes of the subunits in eukaryotic ribosomes?

A

Large subunit = 60S

Small subunit = 40S

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19
Q

Translation

What makes up the small subunit in eukaryotic ribosomes?

A

18S rRNA

33 proteins

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20
Q

Translation

What makes up the large subunit in eukaryotic ribosomes?

A

28S rRNA
5S rRNA
5.8S rRNA
50 proteins

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21
Q

Translation

How are bacterial rRNA genes organised?

A

As a single operon

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22
Q

Translation

How many rRNA genes does the human genome contain?

A

> 200

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23
Q

Translation

How are the 28S, 5.8S and 18S rRNA units coded in the human genome?

A

In a single transcription unit (45S)
Two internally transcribed spaces separate them
5 clusters of them

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24
Q

Translation

What are the clusters of rRNA genes called?

A

Nuclear organiser regions (NORs)

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25
# Translation How does the 5S subunit appear in the human genome?
In tandem arrays On chromosome 1q41-42 Number of repeats is variable
26
# Translation What are the nuclear organiser regions that code for multiple rRNA subunits transcribed by?
RNA polymerase I
27
# Translation What are the tandem arrays of 5S rRNA subunit transcribed by?
RNA polymerase III
28
# Translation What is a pseudoknot?
The extensive tertiary structures formed rRNAs
29
# Translation What is responsible for catalytic reactions within the ribosome?
rRNA
30
# Translation What is the enzymatic function of 28S RNA?
Catalyses the synthesis of peptide bonds between amino acids
31
# Translation What are the rRNA subunits that perform enzymatic functions called?
Ribozymes
32
# Translation What is the enzymatic function of 18S rRNA?
Binds mRNA
33
# Translation What is the site of translation?
rRNA component of ribosome
34
# Translation How does the ribosome know which frame is the open reading frame?
It searches for the initiation codon and reads from there
35
# Translation What is the initiation codon in mRNA and what does it code for?
AUG - methionine
36
# Translation What happens when the ribosomes recognises the initiation codon?
The initiation codon is bound by initiator tRNA
37
# Translation Describe the structure of tRNA
``` 100bp long Complex 4 double stranded stems/arms 3 loop regions Clover leaf structure ```
38
# Translation What are the 4 double stranded arms in tRNA?
Acceptor arm Anticodon arm D arm TΨC arm
39
# Translation Which arm of tRNA doesn't have a loop and what does it have instead?
Acceptor arm | Made up of free 3' end of tRNA
40
# Translation What is the triplet at the 3' end of tRNA that carries amino acids?
CAA
41
# Translation What is the role of the acceptor arm in tRNA?
To carry the amino acid
42
# Translation What is the role of the anticodon loop in tRNA?
Recognises it's complimentary mRNA triplet
43
# Translation What are the roles of the D and T arms in tRNA?
They promote binding
44
# Translation What is eukaryotic tRNA transcribed by?
RNA polymerase III
45
# Translation What are the steps of tRNA transcription?
Endo- and exo-ribonucleases cleave the primary transcript CAA added by tRNA nucletidyl transferase Introns spliced out Bases chemically modified
46
# Translation What is the difference between eukaryotic and prokaryotic tRNA transcription?
Prokaryotic tRNA doesn't need cleaving or splicing
47
# Translation What enzyme adds the CAA codon to the 3' end of tRNA?
tRNA nucletidyl transferase
48
# Translation What do the modifications to the bases in tRNA affect?
Conformation and base pairing
49
# Translation What process does the term "charging" describe when used on tRNA?
The binding of the specific amino acid to its matching tRNA by a equally specific enzyme
50
# Translation What are the enzymes that matches the corresponding amino acid to it's tRNA?
Aminoacyl tRNA synthetases
51
# Translation What does the term tRNA wobble refer to?
When the 1st position of the anticodon (5' end) of tRNA can form a non-standard base pair with sequence of mRNA
52
# Translation What does the term codon bias refer to?
When some codons are used more often than others
53
# Translation What can cause the translation rate to be slower?
Uncommon codons called choke points
54
# Translation What can cause an increased translation rate?
Common codons called Slippery sequences
55
# Translation What can lead to ribosome slip?
Slippery sequences (common codons)
56
# Translation What can happen when a codon slips?
A frameshift in the protein
57
# Translation What could be the effects of a frameshift mutation in translation?
Introduction of STOP codon that causes a truncated protein | Protein sequence altered downstream of the mutation
58
# Translation What mutation doesn't alter the amino acid sequence?
Silent mutations
59
# Translation What mutations add a premature STOP codon?
Nonsense mutations
60
# Translation What mutations alter the amino acid sequence?
Missense mutations
61
# Translation What is the pre-initiation complex?
A free small ribosome subunit binds to the mRNA Accompanied by the initiation tRNA and initiation factors
62
# Translation What makes up the pre-initiation complex?
The small subunit Initiation tRNA Initiation factors
63
# Translation What does the initiation factor IF2 do?
Binds to tRNA
64
# Translation What dos the initiation factor IF3 do?
Recognises AUG start codon | Prevents large subunit prematurely binding
65
# Translation What are the steps of forming the initiation complex in prokaryotes?
``` Initiation factors bind to 30S subunit 16S rRNA anneals to mRNA tRNA binds to initiation codon IF3 is released Large subunit binds IF1 and IF2 are released ```
66
# Translation What is the role of elF2 in eukaryotic translation?
Chaperones tRNA onto the small subunit
67
# Translation What is the role of elF4 in eukaryotic translation?
Loops mRNA | Bridges PABP & mRNA cap
68
# Translation What is the role of elF3 in eukaryotic translation?
Guides looped mRNA into the correct position
69
# Translation What are elF3 and elF4 known as together?
Cap-binding complex
70
# Translation What is the S value of the pre-initiation complex in eukaryotic translation?
48S
71
# Translation How is mRNA recognised in eukaryotic translation?
By its cap structure
72
# Translation What are the steps for forming the initiation complex in eukaryotes?
``` Pre-initiation complex scans downstream of the cap-binding complex tRNA binds to the initiation sequence elF4 released mRNA loop released elF5 mediates binding of large subunit elF2 and elF3 released ```
73
# Translation What is the role of elF5?
Mediates the binding of the large subunit
74
# Translation What are the 3 binding sites on the large subunit?
Aminoacyl site Peptidyl site Exit site
75
# Translation Which part of the ribosome has the 3 binding sites?
The large subunit
76
# Translation What happens in the aminoacyl site in elongation?
Site where the charged tRNA binds to the mRNA
77
# Translation What happens in the peptidyl site in elongation?
The growing peptide chain is carried here
78
# Translation What is the purpose of the exit site in elongation?
Allows the empty tRNAs to exit the ribosome
79
# Translation What elongation factor escorts the aminoacyl tRNA to the A site in prokaryotes?
EF-Tu
80
# Translation What elongation factor escorts the aminoacyl tRNA to the A site in eukaryotes?
Ef-1
81
# Translation What are the steps of enlogation?
Aminoacyl tRNA binds at A site Peptide bond formed between the amino acids in the P site and the A site tRNAs are displaced and mRNA moves one codon sideways compared to ribosome
82
# Translation What mediates ribosome movement in eukaryotes?
EF-2
83
# Translation What mediates ribosome movement in prokaryotes?
EF-G
84
# Translation What are the steps of translation termination?
Ribosome encounters a STOP codon Release factors bind to the A site Peptide cleaved from final tRNA Ribosome dissociates
85
# Translation What release factors are involved in prokaryotic translation termination?
RF1 RF2 RF3
86
# Translation What release factors are involved in eukaryotic translation termination?
eRF1
87
# Translation What can allow termination suppression?
Wobble at stop codon allows the delivery of an amino acid even though it doesn't fully match
88
# Translation Polycistronic mRNA
One mRNA that encodes for several proteins | Each gene has its own Shine-Delgarno sequence, initiation codon and stop codon
89
# Translation What is different about translation with a polycistronic mRNA?
Codes for more than one protein Ribosomes stay attached to mRNA at termination Recruits new tRNA and IFs
90
# Translation Shine-Delgarno sequence
Sequence close to the start of the front of mRNA that is recognised by the ribosome Only found in prokaryotic cells
91
# Translation Kozak sequence
Marks the initiation site on the mRNA in eukaryotic translation
92
# Translation What do proteins pass through if they are destined for the endomembrane or secretion?
Endoplasmic reticulum
93
# Translation What aids with the transportation of newly translated proteins and how?
Signal recognition particles | Bind ribosomes to the ER
94
# Translation How are proteins further modified as they pass through the ER and golgi body?
Folded Cleaved Sugar groups added
95
# Translation When a peptide bond is formed between the amino acid in the A site and the P site, which groups are joined?
The carboxyl group of the amino acid in the P site | The amino group of the amino acid in the A site
96
# Translation What RNA is produced by RNA polymerase I?
rRNA 28S RNA 5.8S RNA 18S RNA
97
# Translation What RNA is produced by RNA polymerase II?
mRNA snRNA miRNA
98
# Translation What RNA is produced by RNA polymerase III?
tRNA 5S rRNA snRNA snoRNA

Molecular Biology & Genetics (8 decks)

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