Selected MCQ

Current Question
Which motor protein transports vesicles toward the plus end of microtubules (generally the cell periphery)?
  • A. Kinesin
  • B. Dynein
  • C. Myosin
  • D. Actin
Correct Answer: A
Explanation:
Kinesin moves cargo anterogradely toward microtubule plus ends (cell periphery). Dynein moves cargo retrogradely (toward minus ends).
Related Question 1
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 2
In Western blotting, proteins are typically detected using:
  • A. DNA probes
  • B. RNA probes
  • C. Enzyme-linked antibodies
  • D. Radioactive amino acids
Correct Answer: C
Explanation:
Western blot uses antibodies (often enzyme-linked) that bind specific proteins on the membrane, allowing visualization via a colorimetric or chemiluminescent reaction.
Related Question 3
SDS-PAGE separates proteins primarily based on:
  • A. Charge only
  • B. Size (molecular weight)
  • C. Hydrophobicity
  • D. Isoelectric point
Correct Answer: B
Explanation:
SDS denatures proteins and coats them with a negative charge that is proportional to their length. In SDS-PAGE, proteins are separated by size; smaller proteins migrate faster.
Related Question 4
Prokaryotic mRNAs often encode multiple proteins on a single transcript. This feature is known as:
  • A. Monocistronic transcription
  • B. Polycistronic transcription
  • C. Post-transcriptional splicing
  • D. Alternative splicing
Correct Answer: B
Explanation:
Polycistronic mRNA contains several open reading frames, each encoding a different protein. This is common in bacteria (e.g., operons).
Related Question 5
Histone deacetylases (HDACs) generally have what effect on gene transcription?
  • A. Increase transcription by opening chromatin
  • B. Repress transcription by condensing chromatin
  • C. Add acetyl groups to histones
  • D. Methylate DNA
Correct Answer: B
Explanation:
HDACs deacetylate histones, reducing positive charge and weakening DNA-histone interactions, thereby condensing chromatin and repressing transcription.