Selected MCQ

Current Question
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 1
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 2
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 3
Two genes exhibit a recombination frequency of 20% in genetic crosses. Which statement is most accurate?
  • A. The genes are likely on different chromosomes
  • B. The genes are roughly 20 map units apart on the same chromosome
  • C. The genes are so far apart that they assort independently
  • D. The genes are allelic variants of each other
Correct Answer: B
Explanation:
A recombination frequency of 20% indicates that the genes are linked (~20 centimorgans apart) on the same chromosome and not assorting completely independently.
Related Question 4
In a pedigree, if two unaffected parents have an affected child, the trait is most likely:
  • A. Autosomal dominant
  • B. Autosomal recessive
  • C. X-linked dominant
  • D. X-linked recessive
Correct Answer: B
Explanation:
Autosomal recessive traits can skip generations. Two carriers (phenotypically normal) can produce an affected child (25% chance).
Related Question 5
Which viral vector carries a high risk of insertional mutagenesis due to genome integration?
  • A. Adenoviral vector
  • B. Retroviral vector
  • C. Adeno-associated viral vector
  • D. Liposome-based vector
Correct Answer: B
Explanation:
Retroviruses integrate their genome into the host DNA. This random insertion can disrupt host genes, increasing the risk of mutagenesis (used with caution in gene therapy).