Selected MCQ

Current Question
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 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 flow cytometry, cells are labeled with fluorescent antibodies and passed in a stream through a laser. This technique primarily measures:
  • A. Cell size and internal complexity
  • B. DNA sequence variants
  • C. Protein structure by X-ray diffraction
  • D. Glycolytic activity
Correct Answer: A
Explanation:
Flow cytometry measures light scattering (size and granularity) and fluorescence from labeled markers, allowing rapid analysis of cell populations (size, complexity, marker expression).
Related Question 3
Pluripotent stem cells are characterized by their ability to:
  • A. Differentiate into all cell types, including extraembryonic membranes
  • B. Differentiate into any cell type of the body (but not extraembryonic tissues)
  • C. Self-renew indefinitely but only become one cell type
  • D. Be harvested from adult muscle tissue
Correct Answer: B
Explanation:
Pluripotent stem cells (like embryonic stem cells) can form any body cell type (endoderm, mesoderm, ectoderm) but cannot form an entire organism (unlike totipotent zygotes).
Related Question 4
Enzyme-linked immunosorbent assay (ELISA) is primarily used to:
  • A. Measure DNA concentration
  • B. Detect specific proteins or antibodies by an enzyme-mediated color change
  • C. Visualize chromosomes under a microscope
  • D. Amplify RNA
Correct Answer: B
Explanation:
ELISA employs enzyme-linked antibodies. When the target antigen or antibody is present, a substrate is converted to a colored product, indicating a positive result.
Related Question 5
Which method uses an electrical pulse to introduce DNA into cells?
  • A. Microinjection
  • B. Electroporation
  • C. Lipofection
  • D. Ultracentrifugation
Correct Answer: B
Explanation:
Electroporation applies a brief high-voltage pulse to permeabilize cell membranes, transiently allowing DNA uptake.