Selected MCQ

Current Question
Which viral vector carries a high risk of insertional mutagenesis due to genome integration?
  • A. Adenoviral vector
  • B. Retroviral vector
  • C. Adeno-associated viral vector
  • D. Liposome-based vector
Correct Answer: B
Explanation:
Retroviruses integrate their genome into the host DNA. This random insertion can disrupt host genes, increasing the risk of mutagenesis (used with caution in gene therapy).
Related Question 1
In gene therapy using a viral vector, what is a major concern related to using retroviruses?
  • A. They cannot infect human cells
  • B. They only integrate into mitochondrial DNA
  • C. Insertional mutagenesis by random integration into the host genome
  • D. They cannot carry large genes
Correct Answer: C
Explanation:
Retroviral vectors integrate randomly into the host genome, risking insertional mutagenesis (disrupting host genes), which can cause cancer or other issues.
Related Question 2
In a cloning vector, what is the purpose of including an antibiotic resistance gene?
  • A. To replicate the plasmid in host cells
  • B. As a selectable marker to identify transformed cells
  • C. To transcribe the cloned gene at high levels
  • D. To initiate DNA replication
Correct Answer: B
Explanation:
The antibiotic resistance gene allows selection: only bacteria that have taken up the plasmid (and express resistance) will grow on antibiotic-containing media.
Related Question 3
A mother carries a mutated X-linked recessive gene but is unaffected. What is the probability that a son of hers will express the trait?
  • A. 0%
  • B. 25%
  • C. 50%
  • D. 100%
Correct Answer: C
Explanation:
A carrier mother (X^mX) has a 50% chance of passing the mutant X to a son. If he receives it, he will express the recessive trait (since sons inherit only one X chromosome).
Related Question 4
HIV is a retrovirus that carries which key enzyme for infection of host cells?
  • A. DNA-dependent DNA polymerase
  • B. Reverse transcriptase
  • C. RNA polymerase III
  • D. Integrase
Correct Answer: B
Explanation:
Retroviruses use reverse transcriptase to copy their RNA genome into DNA, which is then integrated into the host genome.
Related Question 5
In a resting mammalian cell membrane, which ion has the highest permeability and thus most strongly influences the resting membrane potential?
  • A. Sodium (Na+)
  • B. Potassium (K+)
  • C. Chloride (Cl-)
  • D. Calcium (Ca2+)
Correct Answer: B
Explanation:
At rest, cells have many open potassium leak channels, making K+ the most permeable ion. The resting membrane potential is therefore close to the K+ equilibrium potential.