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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