TRB PG Assistant - Translation – initiation, elongation, termination, proofreading, post-translational modifications Online Test (MCQ Quiz)

1. What is the primary function of ribosomes during translation?

A) To synthesize mRNA from a DNA template B) To catalyze the formation of peptide bonds between amino acids C) To transport amino acids to the ribosome D) To unwind the DNA double helix

2. 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)

3. 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

4. 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

5. 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)

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

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

A) Phosphorylation B) Glycosylation C) DNA replication D) Ubiquitination

14. 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

15. 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

16. 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

17. 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

18. 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

19. 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

20. 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

21. 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

22. 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

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

A) eIF1 B) eIF2 C) eIF3 D) eIF4E

24. 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

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

A) Peptidation B) Transpeptidation C) Translocation D) Termination

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. 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

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

A) Hydrogen bond B) Ionic bond C) Peptide bond D) Disulfide bond

29. 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.

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

A) Hydroxylation B) Lipidation C) Sulfation D) N-acetylation

31. 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.

32. 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

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

A) Methylation B) Phosphorylation C) Acetylation D) Ubiquitination

34. 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

35. 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

36. 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

37. 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.

38. 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

39. 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

40. 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

41. 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

42. 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

43. 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

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

A) Glycosylation B) Ubiquitination C) Phosphorylation D) Acetylation

45. 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

46. 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

47. 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

48. 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

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

A) Phosphorylation B) Acetylation C) Glycosylation D) Methylation

50. 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

Translation – initiation, elongation, termination, proofreading, post-translational modifications - Online Test

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