Molecular Biology MCQs

1. What is the function of a ribosome in a cell? A) To store genetic information B) To transcribe DNA C) To translate mRNA into proteins D) To replicate DNA Answer: C) To translate mRNA into proteins 2. What is the role of a promoter in gene expression? A) To terminate mRNA transcription B) To signal the start of mRNA transcription C) To facilitate translation of mRNA D) To regulate protein folding Answer: B) To signal the start of mRNA transcription 3. Which enzyme is responsible for adding nucleotides during DNA replication? A) DNA polymerase B) RNA polymerase C) DNA ligase D) Helicase Answer: A) DNA polymerase 4. What is the purpose of DNA methylation in gene regulation? A) To inhibit gene expression B) To enhance gene transcription C) To stabilize mRNA D) To produce ribosomes Answer: A) To inhibit gene expression 5. Which of the following is an example of a point mutation? A) Insertion of a nucleotide B) Deletion of a gene C) Substitution of one nucleotide for another D) Duplication of a chromosome Answer: C) Substitution of one nucleotide for another 6. What is the function of a restriction enzyme in molecular biology? A) To replicate DNA B) To join DNA fragments together C) To cut DNA at specific sequences D) To proofread DNA Answer: C) To cut DNA at specific sequences 7. Which of the following is NOT a component of a typical eukaryotic gene? A) Promoter B) Exon C) Intron D) Repressor Answer: D) Repressor 8. What is the role of a transcription factor in gene expression? A) To transcribe mRNA B) To inhibit protein synthesis C) To regulate gene transcription by binding to DNA D) To catalyze biochemical reactions Answer: C) To regulate gene transcription by binding to DNA 9. What is a codon in the context of genetic code? A) A sequence of three nucleotides that codes for a protein B) A sequence of three amino acids C) A stop signal for protein synthesis D) An RNA molecule Answer: A) A sequence of three nucleotides that codes for a protein 10. Which of the following is involved in post-translational modification of proteins? A) Ribosome B) Golgi apparatus C) Nucleus D) Endoplasmic reticulum Answer: B) Golgi apparatus 11. What is the function of miRNAs in gene regulation? A) To promote gene transcription B) To enhance translation of mRNA C) To inhibit translation of mRNA D) To produce ribosomes Answer: C) To inhibit translation of mRNA 12. What is RNA interference (RNAi) used for in molecular biology? A) To amplify DNA B) To silence gene expression C) To replicate RNA D) To sequence DNA Answer: B) To silence gene expression 13. What is the role of a plasmid in molecular biology? A) To store genetic information in bacteria B) To transcribe mRNA C) To translate proteins D) To proofread DNA Answer: A) To store genetic information in bacteria 14. Which of the following is a characteristic of a eukaryotic cell? A) Presence of a nucleus B) Presence of a cell wall made of peptidoglycan C) Absence of membrane-bound organelles D) Presence of a single circular chromosome Answer: A) Presence of a nucleus 15. What is the function of a ribozyme in molecular biology? A) To synthesize RNA B) To catalyze biochemical reactions C) To produce ribosomes D) To store genetic information Answer: B) To catalyze biochemical reactions 16. Which enzyme is responsible for joining Okazaki fragments on the lagging strand during DNA replication? A) DNA polymerase B) RNA polymerase C) DNA ligase D) Helicase Answer: C) DNA ligase 17. What is the role of telomeres in DNA replication? A) To initiate replication B) To prevent degradation of the chromosome ends C) To unwind the DNA double helix D) To proofread DNA Answer: B) To prevent degradation of the chromosome ends 18. Which of the following is a function of the 5′ cap and poly-A tail in mRNA? A) To stabilize mRNA B) To facilitate translation C) To inhibit transcription D) To degrade mRNA Answer: A) To stabilize mRNA 19. What is the function of an operon in gene regulation? A) To inhibit gene expression B) To regulate multiple genes as a unit C) To synthesize proteins D) To replicate DNA Answer: B) To regulate multiple genes as a unit 20. Which process involves the removal of introns and joining of exons in pre-mRNA? A) Transcription B) Translation C) Splicing D) Replication Answer: C) Splicing 21. What is the function of a promoter in transcription? A) To terminate mRNA synthesis B) To signal the start of mRNA synthesis C) To code for amino acids D) To produce ribosomes Answer: B) To signal the start of mRNA synthesis 22. Which of the following is true about gene expression? A) It is the process of DNA replication B) It involves the synthesis of proteins from mRNA C) It occurs in the nucleus of a cell D) It is regulated by tRNA Answer: B) It involves the synthesis of proteins from mRNA 23. What is the role of a transcription factor in gene regulation? A) To inhibit gene transcription B) To promote translation of mRNA C) To regulate gene transcription by binding to DNA D) To catalyze biochemical reactions Answer: C) To regulate gene transcription by binding to DNA 24. What is the function of reverse transcriptase in molecular biology? A) It synthesizes DNA from RNA B) It synthesizes RNA from DNA C) It transcribes mRNA D) It translates proteins Answer: A) It synthesizes DNA from RNA 25. What is the significance of gel electrophoresis in molecular biology? A) It amplifies DNA fragments B) It separates DNA or RNA fragments based on size C) It replicates RNA D) It produces ribosomes Answer: B) It separates DNA or RNA fragments based on size 26. What is the central dogma of molecular biology? A) DNA replication B) RNA transcription C) Protein translation D) All of the above Answer: D) All of the above 27. Which of the following is NOT a component of a nucleotide? A) Phosphate group B) Sugar molecule C) Nitrogenous base D) Amino acid Answer: D) Amino acid 28. What is the complementary DNA sequence to 5′-ATCGTA-3′? A) 5′-CGATAC-3′ B) 5′-UAGCAU-3′ C) 3′-TAGCAT-5′ D) 3′-GCATAG-5′ Answer: A) 5′-CGATAC-3′ 29. Which enzyme is responsible for unwinding the DNA double helix during replication? A) DNA polymerase B) DNA ligase C) Helicase D) RNA polymerase Answer: C) Helicase 30. What is the function of DNA polymerase in DNA replication? A) It adds nucleotides to the new DNA strand B) It seals the gaps between Okazaki fragments C) It proofreads and corrects errors in DNA D) All of the above Answer: D) All of the above 31. What is the role of mRNA in protein synthesis? A) It carries amino acids to the ribosome B) It serves as the template for DNA replication C) It carries the genetic code from DNA to the ribosome D) It forms the backbone of the ribosome Answer: C) It carries the genetic code from DNA to the ribosome 32. Which of the following is true about tRNA (transfer RNA)? A) It carries amino acids to the ribosome during translation B) It forms the backbone of the DNA double helix C) It transcribes DNA into RNA during replication D) It is the primary site of protein synthesis Answer: A) It carries amino acids to the ribosome during translation 33. What is the start codon that initiates protein synthesis? A) AUG B) UAA C) CCC D) GGG Answer: A) AUG 34. What is the process by which mRNA is made from a DNA template? A) Transcription B) Translation C) Replication D) Transformation Answer: A) Transcription 35. Which enzyme is responsible for transcribing mRNA from a DNA template? A) DNA polymerase B) RNA polymerase C) Helicase D) Ligase Answer: B) RNA polymerase 36. What is the function of ribosomes in protein synthesis? A) They produce mRNA B) They synthesize DNA C) They decode the mRNA to assemble amino acids into proteins D) They replicate DNA Answer: C) They decode the mRNA to assemble amino acids into proteins 37. What is the role of the promoter region in transcription? A) It terminates transcription B) It signals the start of transcription C) It codes for amino acids D) It produces mRNA Answer: B) It signals the start of transcription 38. What is alternative splicing in eukaryotic gene expression? A) The removal of introns from mRNA B) The synthesis of multiple proteins from a single gene C) The replication of DNA D) The translation of mRNA into proteins Answer: B) The synthesis of multiple proteins from a single gene 39. What is a codon? A) A sequence of three amino acids B) A sequence of three nucleotides in mRNA that codes for an amino acid C) A region of DNA that regulates gene expression D) A protein that catalyzes biochemical reactions Answer: B) A sequence of three nucleotides in mRNA that codes for an amino acid 40. Which of the following is a post-transcriptional modification of mRNA? A) Addition of a poly-A tail B) Removal of introns C) Addition of a 5′ cap D) All of the above Answer: D) All of the above 41. What is the function of miRNA (microRNA) in gene regulation? A) It promotes gene transcription B) It inhibits translation of mRNA C) It splices pre-mRNA D) It produces ribosomes Answer: B) It inhibits translation of mRNA 42. What is the primary function of DNA helicase during replication? A) It synthesizes new DNA strands B) It unwinds the DNA double helix C) It proofreads DNA for errors D) It repairs damaged DNA Answer: B) It unwinds the DNA double helix 43. What is the role of telomerase in DNA replication? A) It synthesizes telomeres at the ends of chromosomes B) It unwinds DNA strands C) It proofreads DNA for errors D) It repairs damaged DNA Answer: A) It synthesizes telomeres at the ends of chromosomes 44. What is the function of DNA ligase in DNA replication? A) It unwinds the DNA double helix B) It proofreads DNA for errors C) It joins Okazaki fragments on the lagging strand D) It synthesizes new DNA strands Answer: C) It joins Okazaki fragments on the lagging strand 45. What is the role of topoisomerase in DNA replication? A) It synthesizes DNA strands B) It unwinds the DNA double helix C) It prevents supercoiling of DNA D) It proofreads DNA for errors Answer: C) It prevents supercoiling of DNA 46. What is the function of reverse transcriptase in molecular biology? A) It synthesizes DNA from RNA B) It synthesizes RNA from DNA C) It transcribes mRNA D) It translates proteins Answer: A) It synthesizes DNA from RNA 47. What is the purpose of gel electrophoresis in molecular biology? A) To visualize proteins B) To separate DNA or RNA fragments based on size C) To synthesize new DNA strands D) To amplify DNA sequences Answer: B) To separate DNA or RNA fragments based on size 48. Which of the following is NOT a type of RNA found in cells? A) mRNA (messenger RNA) B) tRNA (transfer RNA) C) rRNA (ribosomal RNA) D) dRNA (deoxyribonucleic RNA) Answer: D) dRNA (deoxyribonucleic RNA)

Molecular Biology MCQs

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