Translation

Question 1

Base triplets that are read by the ribosome:

Answer 1

Codons

Question 2

Degeneracy refers to:

Answer 2

some amino acids having more than one codon.

Question 3

Start codon:

Answer 3

AUG

Question 4

AUG is the only codon for this amino acid.

Answer 4

methionine

Question 5

Stop codons:

Answer 5

UAA
UGA
UAG

Question 6

UGA is an initiation/termination factor.

Answer 6

Termination

Question 7

Open reading frame (ORF) is referred to:

Answer 7

The in-frame sequence between the start and stop codons.

Question 8

N-terminus of a protein corresponds to the ____ end of the mRMA.

Answer 8

5’

Question 9

3’ end of the nRMA corresponds to _____ of the protein.

Answer 9

C-terminus

Question 10

Which amino acids have only 1 codon?

Answer 10

Met and Trp

Question 11

Prokeryotic subunits are:

Answer 11

Ribosome = 70S
Large subunit = 50S
Small subunit = 30S

Question 12

Eukaryotic ribosome subunits:

Answer 12

80S

Question 13

60S is the large subunit for _____.

Answer 13

Eukaryotes

Question 14

Eukaryotic subunits are:

Answer 14

Ribosome = 80S
Large subunit = 60S
Small subunit = 40S

Question 15

List the 5 major stages of protein synthesis:

Answer 15

1. Activation of Amino acids
2. Initiation
3. Elongation
4. Termination and ribosome recycling
5. Folding and posttranslational processing

Question 16

What does the “charging” of an amino acid mean?

Answer 16

When amino acids are attached to the 3’ OH of the corresponding tRNA via ester bonds.

Question 17

Enzyme involved in tRNA charging:

Answer 17

amino acyl-tRNA synthetase

Question 18

Charging the tRNA for amino acid activation step of protein synthesis is reversible. (T/F)

Answer 18

False; 2 high energy bonds are used -> irreversible.

Question 19

Overall rxn of tRNA charging:

Answer 19

AA + tRNA + ATP -> AA-tRNA + AMP + PPi

Question 20

Initiation of protein synthesis in bacteria needs these components:

Answer 20

1. 30S ribosomal subunit
2. mRNA
3. Initiating fMet-tRNA
4. IF-1/2/3
5. GTP
6. 50S ribosomal subunit
7. Mg2+

Question 21

What is the first step of initiation complex synthesis?

Answer 21

30S subunit binds to mRNA on the start codon at the P site

Question 22

How is initiation codon distinguished in bacterial mRNA?

Answer 22

By its proximity to Shine-Dalgarno sequence

Question 23

In step 2 of bacterial Initiation complex:

Answer 23

fMet-tRNA binds to P site of 30S and the anticodon is paired with the start codon of mRNA

Question 24

fMet-tRNA will only bind to ___ site of 30S.

Answer 24

P

Question 25

Describe step 3 of the bacterial Initiation complex synthesis.

Answer 25

• 50S subunit binds to initiation complex.
• GTP->GDP on IF-2
• IF-1/2/3 released from the complex
• Initiator tRNA is bound to P side and A site is empty.

Question 26

During elongation stage of protein synthesis movement of ribosome along mRNA is:

Answer 26

from 5’ to 3’

Question 27

What are the requirements for bacterial elongation?

Answer 27

• Initiation complex
• Next aminoacyl-tRNA
• Elongation factors

Question 28

List the steps of bacterial elongation in protein synthesis:

Answer 28

1. Binding of next aminoacyl-tRNA to A site of 70S subunit
2. Peptide bond formation bw 2 amino acids by peptidyl transferase
3. Translocation of the ribosome on the mRNA ONE codon towards the 3’ end.

Question 29

During ______, A and E sites cannot be occupied simultaneously.

Answer 29

Elongation stage of protein synthesis

Question 30

Protein synthesis is inhibited by:

Answer 30

antibiotics and toxins

Question 31

Name the inhibitors of translation:

Answer 31

• Tetracyclines
• Chloramphenicol
• Streptomycin
• Aminoglycosides
• Macrolides
• Cycloheximide
• Diptheria toxin
• Ricin