Selected MCQ

Current Question
An ER-resident protein contains a C-terminal KDEL sequence. If this sequence is missing, what would likely happen to the protein?
  • A. It would be transported to the Golgi
  • B. It would be secreted from the cell
  • C. It would remain in the cytosol
  • D. It would be targeted to mitochondria
Correct Answer: B
Explanation:
KDEL is an ER retention signal. Without KDEL, the protein is not retrieved from the Golgi and is secreted.
Related Question 1
A newly synthesized protein is destined for secretion outside the cell. Which sequence or signal will it most likely contain?
  • A. A hydrophobic transmembrane domain
  • B. A nuclear localization signal
  • C. A signal peptide at the N-terminus
  • D. A peroxisomal targeting signal at the C-terminus
Correct Answer: C
Explanation:
Secreted proteins typically have an N-terminal signal peptide that directs the ribosome to the ER for co-translational translocation into the secretory pathway.
Related Question 2
A one-nucleotide insertion in the coding sequence of a gene will most likely result in which type of mutation?
  • A. Missense mutation
  • B. Nonsense mutation
  • C. Frameshift mutation
  • D. Silent mutation
Correct Answer: C
Explanation:
Inserting one nucleotide shifts the reading frame of the codons (frameshift), altering all downstream amino acids and usually disrupting function.
Related Question 3
Overexpression of the Bcl-2 protein in a cell would most likely result in which effect?
  • A. Increased apoptosis
  • B. Enhanced autophagy
  • C. Resistance to apoptosis
  • D. Increased necrosis
Correct Answer: C
Explanation:
Bcl-2 is an anti-apoptotic protein. Its overexpression makes cells more resistant to apoptotic signals, promoting cell survival.
Related Question 4
Which assay would you use to detect and quantify a specific DNA sequence in a sample?
  • A. ELISA
  • B. Southern blot
  • C. Western blot
  • D. Gram staining
Correct Answer: B
Explanation:
A Southern blot uses a DNA probe to hybridize with a specific DNA sequence immobilized on a membrane, allowing detection of that sequence in the sample.
Related Question 5
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.