Gene Translation Flashcards
1
Q
Where its lots of gene translation taking place?
A
In the RER
2
Q
What are the 3 types of RNA?
A
- rRNA (ribosomal RNA)
- mRNA
- tRNA
3
Q
What % of RNA is rRNA?
A
> 80%
4
Q
What makes rRNA?
A
RNA polymerase I
5
Q
What % of RNA is mRNA?
A
~2%
6
Q
What is mRNA made by?
A
RNA polymerase II
7
Q
What % of RNA is tRNA?
A
~15%
8
Q
What makes tRNA?
A
RNA polymerase III
9
Q
How many kinds of rRNA are there?
A
Only 4 or 5
10
Q
How is there such a high % of rRNA with so few types?
A
Many copies or each
11
Q
How many types of mRNA are there?
A
100,000s
12
Q
How many copies are there of each mRNA?
A
Only a few
13
Q
How are there so many types of mRNA?
A
Because genes can make more than one mRNA each
14
Q
How can genes make more than one type of mRNA each?
A
Because splicing can be used to add another layer of complexity of gene regulation
15
Q
Give an example of how splicing could be used to add complexity?
A
Sometimes an intron could be spliced out, sometimes it could be left in
16
Q
How many types of tRNA are there?
A
~100
17
Q
How many copies are there of each type of tRNA?
A
Very many
18
Q
How many rRNAs are there in the ribosomes of prokaryotes?
A
3
19
Q
How many proteins are there in the ribosomes of prokaryotes?
A
56
20
Q
What sub-units are in the ribosomes of prokaryotes?
A
30s and 50s
21
Q
What ribosomes do prokaryotes have?
A
70s
22
Q
How many rRNAs are there in the ribosomes of eukaryotes?
A
4
23
Q
How many proteins are there in the ribosomes of eukaryotes?
A
82
24
Q
What sub-units are there in the ribosomes of eukaryotes?
A
40s + 60s
25
What ribosomes do eukaryotes have?
80s
26
Why is translation more tricky that transcription?
- Changing nucleotides to amino acids
| - 4 letter code to 20 letter code
27
What does translation require?
An adaptor molecule
28
Describe the features of the genetic code
#NAME?
29
What is the result of ‘changing the language’ in translation?
5’ to 3’ template read-through producing N to C template extension
30
What is the adaptor molecule used in translation?
tRNA
31
What are the initiation codons?
Methionine- AUG
32
What are the termination codons?
#NAME?
33
What is tRNAs structure?
Clover model
34
How is the specific clover model of tRNA produced?
Complementary antiparallel sequences form hydrogen bonds, forming stem loops
35
What does each tRNA have?
An anticodon
36
What does the anticodon consist of?
3 bases
37
Is tRNA charged or uncharged?
Can be either
38
What does tRNA being charged mean?
It has energy
39
What can tRNA do when its charged?
Have an amino acid connected to it
40
What is tRNA called when it has an amino acid connected to it?
An amino acyl tRNA
41
What does the name of the tRNA change depending on?
Which amino acid is connected
42
What do anticodons recognise?
mRNA codons that are complementary
43
What base can anticodons have?
I- inosine
44
Why might tRNA have I?
It is aspecific, and so one tRNA can recognise different codons for the same amino acid
45
What is known as the ‘wobble position’?
The 5’ base of anticodon, and hence the 3’ base of the codon
46
What is the purpose of the wobble position?
It allows a single tRNA species to recognise more than one codon
47
Does it matter what base is in the wobble position?
Often, no
48
What base will I not bond with?
G
49
What happens in initiation of translation?
AUG codon recognition
50
What recognises the AUG codon?
A ‘special’ methionyl tRNA ribosome
51
In what direction is the strand elongated in translation?
N to C
52
What are the building blocks in gene translation?
Aminoacyl tRNAs
53
When does translation terminate?
When it reaches a stop codon
54
What is each aminoacyl tRNA synthase specific for?
A specific amino acid
55
What binds to tRNA synthase?
The amino acid and ATP
56
What happens to the ATP once binded to tRNA?
It is converted to pyrophosphate, then phosphate, with AMP still attached to the enzyme
57
What happens once the ATP has been converted to phosphate on the tRNA synthase?
tRNA attaches to the enzyme, releasing AMP
58
What happens once AMP has been released from the tRNA synthase-tRNA complex?
Aminoacyl tRNA is released
59
What has happened once aminoacyl tRNA has been released?
The amino acid has been activated
60
What is recognised in initiation of translation?
The 5’ cap of the mature mRNA
61
What recognises the 5’ cap of the mature mRNA in initiation of translation?
Cap binding proteins, initiation factors and tRNA
62
What attaches to the 5’ cap of the mRNA?
The 40s sub unit of tRNA
63
Does the binding of the 40s sub unit of the tRNA to the 5’ cap require energy?
Yes, in the form of GTP
64
What happens once the 40s sub unit has bound to the 5’ cap?
It moves along until it finds the first codon
65
Does the movement of the 40s sub unit to the first codon require energy?
Yes, in the form of ATP
66
What happens once the 40s sub unit has found the first codon?
The 60s sub unit binds
67
What happens when the 60s sub unit of tRNA binds to the 40s at the first codon?
GDP, initiation factors and cap binding proteins are released, making a fully functioning ribosome
68
What sites are available at the newly functional ribosome?
A site and P site
69
Where does aminoacyl-tRNA bind in elongation during translation?
To the empty A site of the ribosome
70
What is the binding of aminoacyl-tRNA to the A site of the ribosome dependant on?
Energy in the form of GTP
71
What is formed between the two amino acids on the ribosome in translation?
A peptide bond
72
What is the result of the formation of a peptide bond between the two amino acids in the ribosome?
It frees up the P site
73
What happens once the peptide bond has resulting in the freeing of the P site?
The ribosome moves along
74
What is the process of the ribosome moving along called?
Translocation
75
Does translocation require energy?
Yes, in the form of GTP
76
What is the result of translocation?
The A site is now empty, and the cycle can continue
77
What is peptidyl transferase?
The enzyme that makes peptide bonds
78
What does peptidyl transferase do with regards to the P and A sites?
Moves the amino acid bound to the tRNA on the P site onto the amino acid bound to tRNA on the A site, and peptide bonds them together
79
What does peptidyl transferase produce?
Uncharged tRNA and peptidyl-tRNA
80
Why does peptidyl transferase produce peptidyl-tRNA?
As the tRNA now has more than one amino acid attatched
81
How is translation terminated?
A stop codon in the A site
82
What is the effect of a stop codon in the A site?
Means water will bind with the peptidyl-tRNA in the P site, forming peptide and tRNA, hence terminating translation
83
What are the differences between human and bacterial gene expression?
Bateria have-
- Simple promoters
- Different transcription factors
- Single RNA polymerase
- Coupled transcription-translation
- No post-transcriptional processing
- Short lived mRNAs
- Simpler ribosomes
- Distinctive translation initiation mechanism
- Different translation factors
