Selected MCQ

Current Question
Fluorescence in situ hybridization (FISH) is a technique used to:
  • A. Fragment DNA into smaller pieces
  • B. Visualize specific DNA or RNA sequences in cells or chromosomes using fluorescent probes
  • C. Measure protein concentration in solution
  • D. Separate DNA by size
Correct Answer: B
Explanation:
FISH uses fluorescently labeled probes that hybridize to specific DNA sequences on chromosomes or cells, allowing localization under a fluorescence microscope.
Related Question 1
Which plasmid-based technique is used to enrich and detect low-abundance mRNAs by reverse transcription into cDNA?
  • A. RFLP analysis
  • B. Northern blotting
  • C. RT-PCR (reverse-transcription PCR)
  • D. Affinity chromatography
Correct Answer: C
Explanation:
RT-PCR involves reverse-transcribing RNA to cDNA and then amplifying specific sequences by PCR. It is very sensitive for detecting low-abundance transcripts.
Related Question 2
Which chromatography technique separates proteins primarily based on size using a gel matrix?
  • A. Ion-exchange chromatography
  • B. Gel filtration (size-exclusion) chromatography
  • C. Affinity chromatography
  • D. Reverse-phase chromatography
Correct Answer: B
Explanation:
Gel filtration chromatography (size-exclusion) separates proteins by size: larger molecules elute first because they enter fewer pores in the matrix, while smaller molecules elute later.
Related Question 3
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 4
In Southern blotting, what type of probe is used to detect specific DNA sequences?
  • A. DNA probe labeled with a reporter
  • B. RNA probe labeled with a reporter
  • C. Protein probe labeled with antibody
  • D. Carbohydrate probe
Correct Answer: A
Explanation:
Southern blot uses a labeled single-stranded DNA (or RNA) probe complementary to the target DNA sequence, hybridizing to it on the membrane.
Related Question 5
The technique for producing monoclonal antibodies involves fusing a specific antibody-producing B cell with a myeloma cell (a cancer cell). This hybrid cell line is called a:
  • A. Bacteriophage
  • B. Hybridoma
  • C. Plasmid
  • D. Complement
Correct Answer: B
Explanation:
A hybridoma results from fusing a single B lymphocyte (which produces one antibody) with a myeloma cell, creating an immortal cell line that produces identical (monoclonal) antibodies.