Selected MCQ

Current Question
The insulin receptor has intrinsic kinase activity. Upon insulin binding, which type of residue on the receptor is autophosphorylated?
  • A. Serine
  • B. Threonine
  • C. Tyrosine
  • D. Glycine
Correct Answer: C
Explanation:
The insulin receptor is a tyrosine kinase. Upon ligand binding, it autophosphorylates tyrosine residues on its cytoplasmic domain.
Related Question 1
Which type of endocytosis involves clathrin-coated pits and often requires receptor binding?
  • A. Phagocytosis
  • B. Pinocytosis
  • C. Receptor-mediated endocytosis
  • D. Exocytosis
Correct Answer: C
Explanation:
Receptor-mediated endocytosis uses clathrin-coated vesicles. Specific ligands bind membrane receptors, concentrating them in coated pits for internalization.
Related Question 2
Binding of extracellular matrix protein fibronectin to a cell’s integrin receptor most directly triggers which intracellular signaling pathway?
  • A. cAMP/PKA pathway
  • B. MAP kinase (ERK) pathway
  • C. JAK/STAT pathway
  • D. Hedgehog signaling pathway
Correct Answer: B
Explanation:
Integrin activation often activates focal adhesion kinase and the MAPK/ERK cascade, promoting cell survival and proliferation.
Related Question 3
Human insulin production by recombinant DNA technology was first achieved in:
  • A. Yeast cells
  • B. Bacterial cells
  • C. Mammalian cells
  • D. Plant cells
Correct Answer: B
Explanation:
The first human protein successfully produced by genetic engineering was insulin, expressed in genetically modified Escherichia coli bacteria.
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
Down syndrome (trisomy 21) results in how many total chromosomes in a karyotype?
  • A. 45
  • B. 46
  • C. 47
  • D. 48
Correct Answer: C
Explanation:
Down syndrome is caused by an extra copy of chromosome 21. Humans normally have 46 chromosomes; trisomy adds one extra, making 47.