Selected MCQ

Current Question
One major difference between intermediate filaments and microtubules is that intermediate filaments:
  • A. Contain α- and β-tubulin
  • B. Are polar structures
  • C. Degrade in the absence of ATP
  • D. Lack structural polarity
Correct Answer: D
Explanation:
Intermediate filaments are apolar (no distinct plus/minus ends) and do not require nucleotide hydrolysis for polymerization.
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
Gap junction channels between animal cells are formed by which protein?
  • A. Connexin
  • B. Cadherin
  • C. Integrin
  • D. Actin
Correct Answer: A
Explanation:
Connexins assemble into connexons that align between adjacent cells to form gap junction channels for direct cytoplasmic communication.
Related Question 3
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 4
Actin filaments (microfilaments) participate in all the following processes except:
  • A. Muscle contraction via interaction with myosin
  • B. Formation of the cleavage furrow during cytokinesis
  • C. Rapid, long-range vesicle transport along axons via kinesin
  • D. Structural support of microvilli in intestinal epithelial cells
Correct Answer: C
Explanation:
Actin is key in muscle contraction, cytokinesis, and microvilli structure. Kinesin motors move along microtubules, not actin, for long-range vesicle transport.
Related Question 5
A mutation prevents dynein from binding microtubules in eukaryotic cells. Which of the following processes would be most directly impaired?
  • A. Skeletal muscle contraction
  • B. Movement of vesicles from the Golgi apparatus to the endoplasmic reticulum
  • C. Movement of chromosomes toward the spindle poles during mitosis
  • D. Sliding of microtubule doublets in eukaryotic cilia and flagella
Correct Answer: D
Explanation:
Dynein motor proteins drive the sliding of microtubule doublets in cilia and flagella. Without functional dynein, ciliary and flagellar motion would be impaired. (Other processes involve myosin or different motor proteins.)