L21 Translation

Question 1

In translation mRNA is used as a template for the…

Answer 1

Production of a polypeptide

Question 2

Three 3 key characteristics of the genetic code are…

Answer 2

1. Triplet code
2. Non-overlapping
3. Degenerate (redundant)

Question 3

The genetic code is degenerate, which means one amino acid can be encoded…

Answer 3

By more than one codon

Question 4

Different codons which code for the same amino acid are known as…

Answer 4

Synonymous codons

Question 5

61 codons specify…

Answer 5

Amino acids

Question 6

3 codons specify…

Answer 6

Stop

Question 7

The stop codons are…

Answer 7

UAA, UAG, UGA

Question 8

AUG codes for which amino acid?

Answer 8

Methionine

Question 9

The start codon is…

Answer 9

AUG (methionine)

Question 10

The code for amino acids:

a) varies between species
b) is almost universal
c) is universal
d) varies between prokaryotes and eukaryotes

Answer 10

b) is almost universal

There are a few exceptions, for example the stop codon in mitochondria, UGA codes for tryptophan

Question 11

The ‘t’ in tRNA stands for…

Answer 11

Transfer

Question 12

tRNAs form the link between…

Answer 12

RNA and protein

Question 13

The primary structure of tRNAs (4)…

Answer 13

1. Small (70-90nts)
2. 15 invariant residues & 8 semi invariant residues
3. 5’ monophosphate
4. Modified bases (added post-transcription)

Question 14

The modified bases in tRNA are (4)…

Answer 14

1. Ribothymidine (T)
2. Pseudouridine (Ψ)
3. Dihydrouridine (D)
4. Inosine (I) *

*important

Question 15

The secondary structure of tRNAs (5)…

Answer 15

1. D loop
2. I Loop
3. Variable arm
4. Anti-codon loop *
5. Amino Acid acceptor site *

*important

Question 16

Adding amino acids to tRNA is known as the…

Answer 16

Aminoacylation of tRNA

Question 17

Aminoacylation of tRNA results in…

Answer 17

Charged (aminoacyl) tRNAs

Question 18

Aminoacylation of tRNA is a ( 1 / 2 / 3+) step reaction…

Answer 18

2

Question 19

Aminoacylation of tRNAs:

a) Does not require additional energy
b) Is driven by GTP
c) Is driven by ATP
d) Is driven by ADP

Answer 19

c) Is driven by ATP

Question 20

Aminoacylation step 1 forms a high energy intermediate known as…

Answer 20

Aminoacyl Adenylate (AMP + Amino Acid)

Two free phosphates are released from the original ATP

Question 21

In step 2 of aminoacylation, the aminoacyl adenylate reacts with…

Answer 21

A matching tRNA

This forms the aminoacyl tRNA and releases the AMP

Question 22

Amino acids are joined to either the 2’ or 3’ hydroxyls. This doesn’t matter because…

Answer 22

The two forms can freely interconvert

Question 23

Aminoacylation of tRNA involves the enzyme…

Answer 23

Aminoacyl tRNA synthetase (clases I and II)

Question 24

Aminoacyl tRNA synthetase recognises tRNAs based on their…

Answer 24

Identity elements

Question 25

What mechanism allows the aminoacyl tRNA synthetase to differentiate between similar amino acids?

Answer 25

Double-sieve mechanism

Question 26

The double-sieve mechanism involves the acylation site and the editing site, ensuring the amino acid is neither...

Answer 26

Too large or too small

Question 27

serine tRNA is written as...

Answer 27

tRNA^ser | where 'ser' is superscript

Question 28

serine is joined to tRNA^ser by...

Answer 28

Seryl-tRNA synthetase

Question 29

serine + tRNA^ser forms...

Answer 29

ser-tRNA^ser | also known as seryl-tRNA^ser

Question 30

The number of tRNA types is: a) equal to the number of codons b) more than the number of codons c) less than the number of codons

Answer 30

c) less than the number of codons

Question 31

Some tRNAs can recognise multiple codons through...

Answer 31

Wobble base pairing

Question 32

In wobble base pairing the 5' base on the tRNA anticodon forms...

Answer 32

Non-standard base pairs e.g. G - U , I - A, I - C, I - U

Question 33

The difference between class I and class II aminoacyl tRNA synthetases is that they bind...

Answer 33

To different faces of tRNA

Question 34

What are the major feature of tRNA molecules and what are their functions (2)...

Answer 34

1. Anticodon loop (allows binding to matching mRNA codons) | 2. Amino acid acceptor site (binds specific amino acid)