TRB PG Assistant - Translation – initiation, elongation, termination, proofreading, post-translational modifications Question Bank with Options

1. Which of the following is a form of post-translational modification that marks proteins for degradation?

A) Phosphorylation

B) Glycosylation

C) Ubiquitination

D) Acetylation

2. What is the primary role of initiation factors in translation?

A) To catalyze peptide bond formation

B) To bind the initiator tRNA and assemble the ribosomal subunits on the mRNA

C) To recognize stop codons

D) To facilitate the release of the polypeptide chain

3. The process of adding a sugar molecule to a protein is called:

A) Phosphorylation

B) Acetylation

C) Glycosylation

D) Methylation

4. Which of the following is a critical component of the ternary complex that delivers aminoacyl-tRNA to the ribosome during elongation?

A) GTP

B) ATP

C) cAMP

D) cGMP

5. A protein that is destined for secretion or insertion into the plasma membrane typically enters which pathway after synthesis begins?

A) Cytosol

B) Nucleus

C) Endoplasmic reticulum

D) Mitochondria

6. What is the correct order of events at the ribosome during the elongation cycle?

A) tRNA binding, peptide bond formation, translocation

B) Translocation, peptide bond formation, tRNA binding

C) Peptide bond formation, tRNA binding, translocation

D) tRNA binding, translocation, peptide bond formation

7. Which molecule binds to the stop codon on the mRNA and leads to the termination of translation?

A) Initiator tRNA

B) Release factor

C) Elongation factor

D) Ribosomal protein

8. The process of adding a phosphate group to a protein is known as:

A) Glycosylation

B) Ubiquitination

C) Phosphorylation

D) Acetylation

9. What is the function of the A site on the ribosome during elongation?

A) To hold the growing polypeptide chain

B) To release the empty tRNA

C) To bind the incoming aminoacyl-tRNA carrying the next amino acid

D) To bind the mRNA

10. Which type of modification involves the addition of a methyl group, for example, to arginine and lysine residues?

A) Glycosylation

B) Methylation

C) Hydroxylation

D) Acetylation

11. What is the role of the signal recognition particle (SRP) in translation?

A) To initiate translation

B) To terminate translation

C) To target proteins with signal sequences to the endoplasmic reticulum

D) To proofread the mRNA sequence

12. Which of the following is a common mechanism for post-translational control of protein activity?

A) Alternative splicing

B) Capping of mRNA

C) Reversible phosphorylation

D) Polyadenylation

13. What is the function of peptidyl transferase activity within the ribosome?

A) To move the ribosome along the mRNA

B) To hydrolyze the bond between the polypeptide and the tRNA in the P site

C) To catalyze the formation of a peptide bond between the amino acid on the A-site tRNA and the growing polypeptide chain

D) To bind the initiator tRNA

14. Which component is essential for the eukaryotic translation initiation factor (eIF4F) complex to bind to the mRNA 5' cap?

A) eIF2

B) eIF4E

C) eIF5

D) eIF6

15. What is the significance of the anticodon loop on a tRNA molecule?

A) It binds to the amino acid.

B) It binds to the ribosome.

C) It recognizes and binds to the complementary codon on the mRNA.

D) It is involved in proofreading.

16. Post-translational modification can occur in various cellular compartments. Where does N-linked glycosylation primarily occur?

A) Cytosol

B) Nucleus

C) Endoplasmic reticulum and Golgi apparatus

D) Mitochondria

17. Which of the following is a key event in translation termination?

A) Hydrolysis of GTP by elongation factors

B) Binding of a release factor to the A site

C) Formation of the 80S initiation complex

D) Peptide bond formation between amino acids

18. What is the role of elongation factors (e.g., EF-Tu in bacteria, eEF1A in eukaryotes) during translation?

A) To bind stop codons

B) To promote peptide bond formation

C) To facilitate the binding of aminoacyl-tRNAs to the A site

D) To release the completed polypeptide chain

19. Which modification involves the addition of an acetyl group, often to lysine residues on histone proteins?

A) Methylation

B) Phosphorylation

C) Acetylation

D) Ubiquitination

20. The process where a protein folds into its correct three-dimensional structure is crucial for its function and can be aided by:

A) Ligases

B) Isomerases

C) Chaperones

D) Hydrolases

21. What is the function of the Shine-Dalgarno sequence in prokaryotic mRNA?

A) It serves as a stop signal for translation.

B) It is a binding site for RNA polymerase.

C) It is the site where the initiator tRNA binds.

D) It is recognized by the small ribosomal subunit to initiate translation.

22. Which post-translational modification involves the addition of a lipid group to a protein?

A) Hydroxylation

B) Lipidation

C) Sulfation

D) N-acetylation

23. What is the primary difference in initiation between prokaryotic and eukaryotic translation?

A) Prokaryotes use 80S ribosomes, eukaryotes use 70S.

B) Prokaryotes initiate internally, eukaryotes initiate at the 5' cap.

C) Prokaryotes use formylmethionine, eukaryotes use methionine.

D) Prokaryotes use release factors, eukaryotes use termination proteins.

24. Which type of bond is formed between amino acids during translation?

A) Hydrogen bond

B) Ionic bond

C) Peptide bond

D) Disulfide bond

25. What is the role of aminoacyl-tRNA synthetases in translation?

A) To synthesize mRNA

B) To form peptide bonds

C) To charge tRNAs with the correct amino acids

D) To recognize stop codons

26. Which of the following is a common post-translational modification that can regulate protein activity?

A) RNA splicing

B) DNA methylation

C) Acetylation

D) Replication

27. The movement of the ribosome one codon down the mRNA during elongation is called:

A) Peptidation

B) Transpeptidation

C) Translocation

D) Termination

28. What is the function of the E site on the ribosome?

A) To bind the incoming aminoacyl-tRNA

B) To hold the growing polypeptide chain

C) To release the deacylated tRNA

D) To catalyze peptide bond formation

29. Which initiation factor in eukaryotes is responsible for binding the initiator tRNA to the 40S subunit?

A) eIF1

B) eIF2

C) eIF3

D) eIF4E

30. Eukaryotic translation initiation requires the assembly of the 80S ribosome on mRNA. Which subunit initially binds to the mRNA cap?

A) The 40S subunit

B) The 60S subunit

C) The 30S subunit

D) The 50S subunit

31. In prokaryotes, the initiation complex includes:

A) Initiator tRNA, mRNA, 40S ribosomal subunit, initiation factors

B) Initiator tRNA, mRNA, 30S ribosomal subunit, initiation factors

C) Initiator tRNA, mRNA, 60S ribosomal subunit, initiation factors

D) Initiator tRNA, mRNA, 80S ribosomal subunit, initiation factors

32. What is the primary role of chaperones in protein synthesis?

A) To synthesize mRNA

B) To assist in proper protein folding

C) To transport proteins across membranes

D) To degrade misfolded proteins

33. Which process involves the removal of specific amino acid sequences from a polypeptide chain?

A) Acetylation

B) Methylation

C) Proteolytic cleavage

D) Disulfide bond formation

34. What is the role of ubiquitination in post-translational modification?

A) To activate enzymes

B) To signal for protein degradation

C) To facilitate protein folding

D) To increase protein solubility

35. Phosphorylation is the addition of a phosphate group, often to which amino acid residues?

A) Alanine, Glycine, Valine

B) Serine, Threonine, Tyrosine

C) Proline, Leucine, Isoleucine

D) Aspartic acid, Glutamic acid, Cysteine

36. What is glycosylation?

A) The addition of a phosphate group to a protein

B) The addition of a sugar moiety to a protein

C) The addition of a ubiquitin molecule

D) The cleavage of signal peptides

37. Which enzyme is responsible for attaching the correct amino acid to its corresponding tRNA?

A) DNA polymerase

B) RNA polymerase

C) Aminoacyl-tRNA synthetase

D) Peptidyl transferase

38. What is the purpose of proofreading mechanisms during translation?

A) To ensure the correct amino acid is added to the growing polypeptide chain

B) To speed up the rate of translation

C) To prevent ribosome dissociation

D) To modify the mRNA sequence

39. Which of the following is NOT a typical post-translational modification?

A) Phosphorylation

B) Glycosylation

C) DNA replication

D) Ubiquitination

40. What is the function of release factors during translation termination?

A) To recruit new aminoacyl-tRNAs

B) To hydrolyze the polypeptide chain from the last tRNA

C) To bind to the mRNA and stop ribosome movement

D) To catalyze peptide bond formation

41. Which codons are recognized as stop codons in most genetic codes?

A) AUG, UGG, UAG

B) UAA, UAG, UGA

C) GUA, CUC, GAG

D) AUA, UUU, CCC

42. What event signals the termination of translation?

A) Binding of a release factor to a stop codon

B) Recognition of the start codon

C) Depletion of aminoacyl-tRNAs

D) Ribosome dissociation from the mRNA

43. What happens at the P site of the ribosome during elongation?

A) The incoming aminoacyl-tRNA binds

B) The deacylated tRNA exits the ribosome

C) The tRNA holding the growing polypeptide chain is located

D) The mRNA is read

44. The formation of a peptide bond between amino acids is catalyzed by which component of the ribosome?

A) Ribosomal proteins

B) mRNA

C) rRNA (ribozyme activity)

D) tRNA

45. During elongation, where does the incoming aminoacyl-tRNA bind?

A) The P site (Peptidyl site)

B) The E site (Exit site)

C) The A site (Aminoacyl site)

D) The catalytic site

46. What structure allows the ribosome to move along the mRNA molecule during elongation?

A) A Torsional stress mechanism

B) Translocation

C) Reverse transcription

D) Splicing

47. Which subunit of the ribosome is primarily responsible for binding mRNA?

A) The 40S subunit

B) The 60S subunit

C) The 30S subunit (prokaryotes)

D) The 80S subunit (eukaryotes)

48. What is the role of the initiator tRNA during translation initiation in eukaryotes?

A) It carries methionine and recognizes the start codon AUG

B) It carries formylmethionine and recognizes the start codon GUG

C) It carries proline and recognizes the start codon UUU

D) It carries alanine and recognizes the start codon CCU

49. In prokaryotes, translation initiation typically begins with the binding of the ribosome to which sequence on the mRNA?

A) Poly-A tail

B) Shine-Dalgarno sequence

C) TATA box

D) Promoter region

50. Which molecule carries the genetic code from the nucleus to the ribosome?

A) Transfer RNA (tRNA)

B) Ribosomal RNA (rRNA)

C) Messenger RNA (mRNA)

D) Small nuclear RNA (snRNA)

Translation – initiation, elongation, termination, proofreading, post-translational modifications - Question Bank