DNA MCQs With Answer are essential for B. Pharm students preparing for pharmacology, molecular biology and biotechnology exams. This concise, exam-focused set covers DNA structure, replication, transcription, translation, mutation types, repair mechanisms, epigenetics, recombinant DNA techniques and clinically relevant drug–DNA interactions. Practicing targeted DNA MCQs with answers improves conceptual clarity, problem-solving speed and application in drug development, pharmacogenomics and gene therapy. Each question emphasizes pharmaceutical relevance and typical university-level difficulty, helping B. Pharm students master core principles and practical aspects of DNA biology. Answers include brief explanations and references to key techniques like PCR, restriction mapping and sequencing to reinforce learning. Now let’s test your knowledge with 50 MCQs on this topic.
Q1. Which nucleotide base pair is held together by three hydrogen bonds in DNA?
- Adenine–Thymine
- Cytosine–Guanine
- Adenine–Uracil
- Guanine–Thymine
Correct Answer: Cytosine–Guanine
Q2. What is the primary enzyme responsible for synthesizing new DNA strands during replication?
- RNA polymerase
- DNA ligase
- DNA polymerase
- Topoisomerase
Correct Answer: DNA polymerase
Q3. In which direction do DNA polymerases synthesize new DNA strands?
- 5′ to 3′
- 3′ to 5′
- Both directions simultaneously
- Direction is random
Correct Answer: 5′ to 3′
Q4. Which structure is formed at the replication origin where the two strands separate?
- Okazaki fragment
- Replication fork
- Promoter
- Telomere
Correct Answer: Replication fork
Q5. Which enzyme removes RNA primers and replaces them with DNA in prokaryotes?
- DNA polymerase I
- DNA polymerase III
- RNase H
- Primase
Correct Answer: DNA polymerase I
Q6. What are Okazaki fragments?
- Short RNA primers used in leading strand synthesis
- Short DNA segments synthesized on the lagging strand
- Telomeric repeat sequences
- Double-stranded breaks during replication
Correct Answer: Short DNA segments synthesized on the lagging strand
Q7. Which protein prevents reannealing of separated DNA strands during replication?
- Single-strand binding protein (SSB)
- Helicase
- Topoisomerase
- Sliding clamp
Correct Answer: Single-strand binding protein (SSB)
Q8. Which enzyme relieves supercoiling ahead of the replication fork?
- Ligase
- Topoisomerase
- Helicase
- Primase
Correct Answer: Topoisomerase
Q9. Which process synthesizes an RNA copy from a DNA template?
- Translation
- Replication
- Transcription
- Reverse transcription
Correct Answer: Transcription
Q10. Which RNA carries amino acids to the ribosome during translation?
- mRNA
- rRNA
- tRNA
- snRNA
Correct Answer: tRNA
Q11. The codon AUG codes for which amino acid and also serves as what in translation?
- Methionine and stop codon
- Methionine and start codon
- Proline and start codon
- Valine and stop codon
Correct Answer: Methionine and start codon
Q12. Which level of DNA packaging directly involves histone proteins?
- Supercoiling
- Nucleosome formation
- Chromosome condensation via condensin only
- Telomere capping by shelterin complex
Correct Answer: Nucleosome formation
Q13. Which histone modification is most commonly associated with transcriptional activation?
- DNA methylation
- Histone acetylation
- Histone ubiquitination leading to degradation
- Histone crosslinking
Correct Answer: Histone acetylation
Q14. DNA methylation commonly occurs at which dinucleotide in mammalian genomes?
- GpC
- CpG
- ApT
- TpA
Correct Answer: CpG
Q15. Which type of mutation changes a codon to a stop codon?
- Missense mutation
- Nonsense mutation
- Silent mutation
- Frameshift mutation
Correct Answer: Nonsense mutation
Q16. Which DNA repair pathway primarily fixes thymine dimers caused by UV light?
- Base excision repair
- Nucleotide excision repair
- Non-homologous end joining
- Mismatch repair
Correct Answer: Nucleotide excision repair
Q17. Which mechanism repairs double-strand breaks using a homologous template?
- Non-homologous end joining (NHEJ)
- Homologous recombination (HR)
- Base excision repair
- Mismatch repair
Correct Answer: Homologous recombination (HR)
Q18. In PCR, which component provides the starting point for DNA polymerase?
- Template DNA
- Deoxynucleotide triphosphates
- Primers
- Buffer
Correct Answer: Primers
Q19. Which temperature step in PCR is responsible for denaturation of double-stranded DNA?
- Annealing step
- Extension step
- Denaturation step
- Ligase activation step
Correct Answer: Denaturation step
Q20. Which sequencing method is based on chain termination with dideoxynucleotides?
- Next-generation sequencing
- Sanger sequencing
- Nanopore sequencing
- Mass spectrometry sequencing
Correct Answer: Sanger sequencing
Q21. Which feature distinguishes plasmids used in cloning?
- Origin of replication and selectable marker
- Only RNA elements
- Presence of telomeres
- Double-stranded RNA genome
Correct Answer: Origin of replication and selectable marker
Q22. Which enzyme cuts DNA at specific sequences and is essential in recombinant DNA work?
- DNA ligase
- Restriction endonuclease
- RNA polymerase
- Helicase
Correct Answer: Restriction endonuclease
Q23. Which reagent covalently joins DNA fragments during cloning?
- DNA polymerase
- DNA ligase
- Restriction enzyme
- RNase H
Correct Answer: DNA ligase
Q24. Which vector type is commonly used for high-level protein expression in bacteria?
- Shuttle vector without promoter
- Expression vector with strong bacterial promoter
- YAC (yeast artificial chromosome)
- Bacteriophage lambda packaging vector only
Correct Answer: Expression vector with strong bacterial promoter
Q25. Which technique separates DNA fragments based on size by applying an electric field?
- Thin layer chromatography
- Gel electrophoresis
- Mass spectrometry
- ELISA
Correct Answer: Gel electrophoresis
Q26. Which element is necessary in Sanger sequencing to terminate chain elongation?
- dNTPs only
- ddNTPs (dideoxynucleotides)
- DNA ligase
- Topoisomerase
Correct Answer: ddNTPs (dideoxynucleotides)
Q27. Telomerase adds repetitive sequences to chromosome ends; it is a ribonucleoprotein that carries what as a template?
- Protein primer
- RNA template
- DNA template from telomere
- tRNA
Correct Answer: RNA template
Q28. Which class of anticancer drugs intercalates into DNA and can disrupt replication?
- Beta-lactams
- Anthracyclines
- Proton pump inhibitors
- Statins
Correct Answer: Anthracyclines
Q29. Which bacterial enzyme is inhibited by quinolone antibiotics, affecting DNA replication?
- DNA gyrase (topoisomerase II)
- RNA polymerase
- Ribosomal peptidyl transferase
- DNA ligase
Correct Answer: DNA gyrase (topoisomerase II)
Q30. Which element is NOT a component of chromatin?
- Histone proteins
- DNA
- Ribosomal RNA
- Non-histone chromosomal proteins
Correct Answer: Ribosomal RNA
Q31. The wobble hypothesis explains degeneracy of the genetic code at which codon position?
- First position
- Second position
- Third position
- There is no wobble position
Correct Answer: Third position
Q32. Which technique is used to quantify specific DNA sequences in real time during amplification?
- Northern blotting
- qPCR (real-time PCR)
- Southern blotting
- Western blotting
Correct Answer: qPCR (real-time PCR)
Q33. Which element in eukaryotic genes is typically removed from the pre-mRNA during splicing?
- Exons
- Introns
- Promoters
- Enhancers
Correct Answer: Introns
Q34. Which protein complex forms the core of the eukaryotic ribosome’s peptidyl transferase center?
- DNA polymerase
- rRNA within the large ribosomal subunit
- tRNA synthetase
- RNA helicase
Correct Answer: rRNA within the large ribosomal subunit
Q35. In cloning, what is the purpose of a selectable marker gene?
- To initiate transcription
- To allow identification of cells containing the vector
- To increase plasmid replication speed
- To degrade host DNA
Correct Answer: To allow identification of cells containing the vector
Q36. Which repair system corrects base–base mismatches that escape proofreading during replication?
- Nucleotide excision repair
- Mismatch repair
- Homologous recombination
- Direct repair by photolyase
Correct Answer: Mismatch repair
Q37. Antisense oligonucleotides act by which primary mechanism?
- Intercalating into DNA double helix
- Binding complementary mRNA to block translation
- Cleaving DNA at specific sites
- Enhancing ribosomal function
Correct Answer: Binding complementary mRNA to block translation
Q38. Which element is commonly used as a reporter gene in molecular cloning to monitor expression?
- Beta-galactosidase (lacZ)
- DNA polymerase I
- Helicase
- Replication protein A
Correct Answer: Beta-galactosidase (lacZ)
Q39. Which phenomenon describes transfer of genetic material between bacteria via bacteriophages?
- Transformation
- Conjugation
- Transduction
- Transfection
Correct Answer: Transduction
Q40. Which small nuclear RNAs are essential for pre-mRNA splicing in eukaryotes?
- tRNAs
- snRNAs (small nuclear RNAs)
- rRNAs
- miRNAs
Correct Answer: snRNAs (small nuclear RNAs)
Q41. Which term describes changes in gene expression without altering DNA sequence?
- Mutation
- Epigenetic modification
- Transversion
- Point mutation
Correct Answer: Epigenetic modification
Q42. Which viral vector is commonly used for stable gene delivery into dividing and non-dividing cells?
- Adeno-associated virus (AAV)
- Lentivirus
- Retrovirus that cannot integrate
- Bacteriophage lambda
Correct Answer: Lentivirus
Q43. Which enzyme synthesizes short RNA primers during DNA replication?
- Primase
- DNA ligase
- Topoisomerase
- DNA polymerase III
Correct Answer: Primase
Q44. Which DNA lesion results from reactive oxygen species and can lead to GC to TA transversions?
- 8-oxoguanine
- Thymine dimer
- Abasic site (AP site)
- Depurination only
Correct Answer: 8-oxoguanine
Q45. Southern blotting is used to detect which type of biomolecule?
- Proteins
- RNA
- DNA
- Lipids
Correct Answer: DNA
Q46. In pharmacogenomics, DNA variants affecting drug-metabolizing enzymes often occur in which genes?
- CYP450 genes
- Hemoglobin genes
- Collagen genes
- Insulin gene
Correct Answer: CYP450 genes
Q47. Which of the following best defines a plasmid copy number?
- Number of different plasmids in a species
- Average number of plasmid copies per bacterial cell
- Number of plasmid types in a cloning kit
- Number of antibiotic resistance genes on a plasmid
Correct Answer: Average number of plasmid copies per bacterial cell
Q48. Which technique allows detection of specific mRNA levels in tissue samples?
- Southern blot
- Northern blot
- Western blot
- ELISA
Correct Answer: Northern blot
Q49. Which DNA-binding motif is commonly found in transcription factors and recognizes specific DNA sequences?
- Zinc finger motif
- Coiled-coil motif specific to membranes
- Beta-barrel motif for transporters
- Leucine zipper that binds lipids only
Correct Answer: Zinc finger motif
Q50. CRISPR-Cas9 genome editing uses a guide RNA to target DNA; which component mediates the actual DNA cleavage?
- Guide RNA itself
- Cas9 nuclease
- DNA polymerase
- Restriction enzyme from E. coli
Correct Answer: Cas9 nuclease
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