Functions of DNA MCQs With Answer

Introduction: Functions of DNA MCQs With Answer is an essential resource for B. Pharm students studying molecular biology and pharmacogenomics. This concise, keyword-rich guide covers DNA functions such as storage of genetic information, replication, transcription, translation, gene regulation, repair mechanisms, and clinical relevance for drug response. Carefully designed MCQs strengthen understanding of replication enzymes, repair pathways, chromatin structure, mutations, and laboratory techniques like PCR and restriction analysis. Ideal for exam prep and practical learning, these questions connect DNA fundamentals to pharmaceutical applications including pharmacogenetics and drug target discovery. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. Which of the following best describes the primary function of DNA in cells?

• Providing structural support to the cell membrane
• Storing and transmitting genetic information
• Acting as a catalyst in metabolic reactions
• Transporting molecules across organelles

Correct Answer: Storing and transmitting genetic information

Q2. DNA replication is described as semiconservative because:

• Both parental strands remain together after replication
• Each daughter DNA contains one parental and one newly synthesized strand
• Two new strands are synthesized from RNA templates
• The parental DNA is fully conserved and copied multiple times

Correct Answer: Each daughter DNA contains one parental and one newly synthesized strand

Q3. Which enzyme synthesizes RNA primers during DNA replication?

• DNA ligase
• DNA polymerase I
• Primase
• Topoisomerase

Correct Answer: Primase

Q4. The discontinuous synthesis on the lagging strand produces short fragments known as:

• Okazaki fragments
• Primer loops
• Replication bubbles
• Leading fragments

Correct Answer: Okazaki fragments

Q5. Which activity of DNA polymerase allows it to remove incorrectly paired nucleotides during replication?

• 5′ to 3′ polymerase activity
• 3′ to 5′ exonuclease (proofreading) activity
• Ligase activity
• Helicase activity

Correct Answer: 3′ to 5′ exonuclease (proofreading) activity

Q6. Telomerase extends telomeres by adding repeats of which sequence in humans?

• TTAGGG
• AATCCG
• GGGATA
• CCCTAA

Correct Answer: TTAGGG

Q7. Which DNA repair pathway primarily corrects UV-induced pyrimidine dimers?

• Base excision repair (BER)
• Mismatch repair (MMR)
• Nucleotide excision repair (NER)
• Homologous recombination (HR)

Correct Answer: Nucleotide excision repair (NER)

Q8. In prokaryotes, which sequence element is most directly responsible for recruiting RNA polymerase to initiate transcription?

• Shine-Dalgarno sequence
• Promoter
• Operator
• Terminator

Correct Answer: Promoter

Q9. Which of the following is NOT a function of DNA-binding histone proteins?

• Packaging DNA into nucleosomes
• Regulating gene accessibility
• Directly catalyzing transcription
• Contributing to chromatin structure

Correct Answer: Directly catalyzing transcription

Q10. Which type of RNA carries amino acids to the ribosome during translation?

• rRNA
• mRNA
• tRNA
• siRNA

Correct Answer: tRNA

Q11. The central dogma of molecular biology describes flow of information as:

• Protein → DNA → RNA
• DNA → RNA → Protein
• RNA → DNA → Protein
• Protein → RNA → DNA

Correct Answer: DNA → RNA → Protein

Q12. Which enzyme joins Okazaki fragments by forming phosphodiester bonds?

• DNA ligase
• DNA polymerase III
• RNase H
• Topoisomerase II

Correct Answer: DNA ligase

Q13. DNA methylation of cytosine in gene promoter regions typically results in:

• Increased transcriptional activation
• Transcriptional repression or silencing
• Enhanced mRNA splicing
• Protein degradation

Correct Answer: Transcriptional repression or silencing

Q14. Which polymerase synthesizes mRNA in eukaryotic cells?

• DNA polymerase δ
• RNA polymerase II
• RNA polymerase I
• RNA polymerase III

Correct Answer: RNA polymerase II

Q15. Single nucleotide polymorphisms (SNPs) are important in pharmacogenomics because they can:

• Induce immediate cell death in all tissues
• Affect drug metabolism and individual drug response
• Completely prevent DNA replication
• Always result in large chromosomal rearrangements

Correct Answer: Affect drug metabolism and individual drug response

Q16. Reverse transcriptase is used to synthesize:

• Double-stranded genomic DNA from DNA templates
• DNA from an RNA template (cDNA)
• Protein from mRNA
• mRNA from DNA

Correct Answer: DNA from an RNA template (cDNA)

Q17. Which statement about plasmids is TRUE?

• They are linear chromosomal fragments essential for cell survival
• They are extrachromosomal, circular DNA molecules often carrying antibiotic resistance genes
• They code exclusively for ribosomal RNA
• They are only found in eukaryotic nuclei

Correct Answer: They are extrachromosomal, circular DNA molecules often carrying antibiotic resistance genes

Q18. The wobble hypothesis explains how:

• Multiple codons can code for a single amino acid due to flexibility in third base pairing
• All tRNAs pair strictly with a single codon
• DNA replication is error-free
• Ribosomes synthesize proteins without mRNA

Correct Answer: Multiple codons can code for a single amino acid due to flexibility in third base pairing

Q19. Which of the following enzymes relieves supercoiling ahead of the replication fork?

• Primase
• Topoisomerase (gyrase in bacteria)
• DNA ligase
• RNase H

Correct Answer: Topoisomerase (gyrase in bacteria)

Q20. In mismatch repair, which feature allows the repair system to distinguish the newly synthesized strand in bacteria?

• Methylation of the parental strand at GATC sites
• Presence of histones on the new strand
• Length of the Okazaki fragments
• RNA primers left on the parental strand

Correct Answer: Methylation of the parental strand at GATC sites

Q21. Homologous recombination is primarily used by cells to repair which type of DNA damage?

• Single base mismatches
• Double-strand breaks
• Thymine dimers
• Small alkylated bases

Correct Answer: Double-strand breaks

Q22. Which laboratory technique amplifies a specific DNA sequence exponentially?

• Gel electrophoresis
• Western blotting
• Polymerase chain reaction (PCR)
• Chromatography

Correct Answer: Polymerase chain reaction (PCR)

Q23. Restriction endonucleases are useful in molecular cloning because they:

• Synthesize DNA from RNA
• Cut DNA at specific recognition sequences
• Join DNA fragments together
• Replicate plasmids autonomously

Correct Answer: Cut DNA at specific recognition sequences

Q24. Which DNA repair mechanism primarily removes small, non-helix-distorting base lesions such as deaminated bases?

• Nucleotide excision repair (NER)
• Base excision repair (BER)
• Mismatch repair (MMR)
• Non-homologous end joining (NHEJ)

Correct Answer: Base excision repair (BER)

Q25. In eukaryotic genes, introns are removed from pre-mRNA by:

• Ribosomes
• DNA polymerase
• Spliceosome
• Ligase enzymes

Correct Answer: Spliceosome

Q26. Which region of a gene is typically located upstream of the transcription start site and contains binding sites for transcription factors?

• Exon
• Promoter and enhancer regions
• Terminator
• ORF (open reading frame)

Correct Answer: Promoter and enhancer regions

Q27. A nonsense mutation results in:

• Substitution of a single amino acid with another
• Introduction of a premature stop codon
• Insertion of extra amino acids without frame shift
• Synonymous codon change with no amino acid change

Correct Answer: Introduction of a premature stop codon

Q28. Which of the following best describes an operon?

• A eukaryotic chromatin remodeling complex
• A cluster of bacterial genes under control of a single promoter
• A viral mechanism for integrating into the host genome
• A mitochondrial DNA replication site

Correct Answer: A cluster of bacterial genes under control of a single promoter

Q29. Which DNA sequence element in bacteria is recognized by the ribosome to initiate translation?

• Promoter
• Shine-Dalgarno sequence
• Enhancer
• Polyadenylation signal

Correct Answer: Shine-Dalgarno sequence

Q30. Which statement about chromatin structure is correct?

• Euchromatin is tightly packed and transcriptionally inactive
• Heterochromatin is loosely packed and highly active in transcription
• Nucleosomes are composed of DNA wrapped around histone octamers
• DNA methylation always opens chromatin for transcription

Correct Answer: Nucleosomes are composed of DNA wrapped around histone octamers

Q31. Which technique separates DNA fragments based on size using an electric field?

• ELISA
• Gel electrophoresis
• Mass spectrometry
• Flow cytometry

Correct Answer: Gel electrophoresis

Q32. Which of the following best explains the role of enhancers in gene expression?

• Enhancers encode proteins that directly bind RNA polymerase
• Enhancers are DNA elements that increase transcription from a distance
• Enhancers degrade mRNA after transcription
• Enhancers block translation at ribosomes

Correct Answer: Enhancers are DNA elements that increase transcription from a distance

Q33. In bacterial transcription, the sigma factor is responsible for:

• Terminating transcription at stop sites
• Recognizing promoter sequences and facilitating initiation
• Splicing mRNA
• Unwinding DNA during replication

Correct Answer: Recognizing promoter sequences and facilitating initiation

Q34. A frameshift mutation is most likely to result from which type of DNA change?

• Single base substitution
• Insertion or deletion not in multiples of three nucleotides
• Synonymous codon change
• Balanced chromosomal translocation

Correct Answer: Insertion or deletion not in multiples of three nucleotides

Q35. Which enzyme removes RNA primers and replaces them with DNA in prokaryotes?

• DNA polymerase I
• DNA polymerase III
• Primase
• RNase A

Correct Answer: DNA polymerase I

Q36. Pharmacogenetic variability in the CYP450 enzymes primarily affects which aspect of drug therapy?

• Route of administration
• Drug metabolism and clearance
• Color of the pharmaceutical formulation
• Sterility of injectables

Correct Answer: Drug metabolism and clearance

Q37. Which of the following is an example of epigenetic regulation?

• Point mutation in a promoter sequence
• DNA methylation changes affecting gene expression
• Chromosomal deletion removing a gene
• Alternative splicing of pre-mRNA

Correct Answer: DNA methylation changes affecting gene expression

Q38. The anticodon on tRNA pairs with which sequence during translation?

• DNA codon in the nucleus
• mRNA codon in the ribosome
• rRNA catalytic site
• Promoter region of DNA

Correct Answer: mRNA codon in the ribosome

Q39. Non-homologous end joining (NHEJ) differs from homologous recombination because NHEJ:

• Requires a sister chromatid as a template
• Is an error-prone repair that directly ligates broken ends
• Only repairs mismatches
• Always restores the original sequence perfectly

Correct Answer: Is an error-prone repair that directly ligates broken ends

Q40. Which of the following best describes a promoter-proximal element?

• A DNA element located far downstream of the transcription start site
• A regulatory sequence near the promoter that influences transcription initiation
• A sequence found only in mitochondrial DNA
• A short peptide that regulates transcription

Correct Answer: A regulatory sequence near the promoter that influences transcription initiation

Q41. cDNA synthesized from mRNA lacks which of the following features compared to genomic DNA?

• Open reading frames
• Introns
• Exons
• Protein-coding information

Correct Answer: Introns

Q42. Which molecular event directly links genotype to phenotype at the protein level?

• DNA replication speed
• Translation of mRNA into protein
• Chromosome condensation during mitosis
• Telomere shortening

Correct Answer: Translation of mRNA into protein

Q43. A silent mutation is characterized by:

• Change in amino acid sequence leading to nonfunctional protein
• Change in nucleotide sequence that does not change the encoded amino acid
• Insertion of a stop codon
• Deletion causing frameshift

Correct Answer: Change in nucleotide sequence that does not change the encoded amino acid

Q44. Which statement about restriction fragment length polymorphism (RFLP) is true?

• RFLP results from variation in restriction enzyme recognition sites in DNA
• RFLP measures RNA sequence variation
• RFLP always causes disease
• RFLP is unrelated to polymorphic markers

Correct Answer: RFLP results from variation in restriction enzyme recognition sites in DNA

Q45. Which enzyme is essential for removing negative supercoils introduced during transcription?

• DNA helicase
• Topoisomerase
• DNA ligase
• RNA polymerase

Correct Answer: Topoisomerase

Q46. The lac operon in E. coli is an example of gene regulation by:

• Post-translational modification only
• An inducible operon controlled by a repressor and inducer
• Constitutive expression without regulation
• RNA interference mechanisms

Correct Answer: An inducible operon controlled by a repressor and inducer

Q47. Which type of DNA damage is most commonly associated with ionizing radiation?

• Thymine dimers
• Single nucleotide substitutions only
• Double-strand breaks
• Deamination of cytosine

Correct Answer: Double-strand breaks

Q48. MicroRNAs (miRNAs) regulate gene expression primarily by:

• Enhancing DNA replication fidelity
• Binding mRNA to inhibit translation or promote degradation
• Directly modifying histones
• Serving as templates for protein synthesis

Correct Answer: Binding mRNA to inhibit translation or promote degradation

Q49. Which of the following is a direct pharmacological implication of DNA damage repair deficiencies?

• Increased drug solubility in water
• Heightened sensitivity to DNA-damaging chemotherapeutics
• Guaranteed resistance to all antibiotics
• Faster drug absorption from the gut

Correct Answer: Heightened sensitivity to DNA-damaging chemotherapeutics

Q50. In next-generation sequencing, which feature allows massive parallel sequencing of millions of DNA fragments?

• Use of single-molecule protein synthesis
• Clonal amplification and simultaneous sequencing of many fragments
• Exclusive sequencing of RNA without conversion
• Sequencing only one fragment at a time

Correct Answer: Clonal amplification and simultaneous sequencing of many fragments

G S Sachin

I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.

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