Selected MCQ

Current Question
A point mutation changes a codon for an amino acid to a stop codon. This is called a:
  • A. Missense mutation
  • B. Silent mutation
  • C. Nonsense mutation
  • D. Frameshift mutation
Correct Answer: C
Explanation:
Changing an amino acid codon to a stop codon prematurely terminates translation, producing a truncated protein; this is a nonsense mutation.
Related Question 1
A single gene mutation causes both phenylketonuria (affecting skin pigment) and neurological impairment. This phenomenon is called:
  • A. Epistasis
  • B. Pleiotropy
  • C. Codominance
  • D. Penetrance
Correct Answer: B
Explanation:
One gene affecting multiple, seemingly unrelated traits (e.g., PKU’s effects on pigment and brain) is pleiotropy.
Related Question 2
On which end of a tRNA molecule is the amino acid attached during translation?
  • A. 5′ end
  • B. 3′ end
  • C. D-loop
  • D. Anticodon loop
Correct Answer: B
Explanation:
The 3′-terminal CCA sequence of tRNA is where aminoacyl-tRNA synthetases covalently attach the amino acid.
Related Question 3
The checkpoint that verifies DNA is completely replicated and undamaged before a cell enters mitosis is called:
  • A. G1/S checkpoint
  • B. S-phase checkpoint
  • C. G2/M checkpoint
  • D. Spindle assembly checkpoint
Correct Answer: C
Explanation:
The G2/M checkpoint ensures that all DNA has been accurately replicated and that any damage is repaired before mitosis. If errors are found, the cycle is halted for repair.
Related Question 4
The technique for producing monoclonal antibodies involves fusing a specific antibody-producing B cell with a myeloma cell (a cancer cell). This hybrid cell line is called a:
  • A. Bacteriophage
  • B. Hybridoma
  • C. Plasmid
  • D. Complement
Correct Answer: B
Explanation:
A hybridoma results from fusing a single B lymphocyte (which produces one antibody) with a myeloma cell, creating an immortal cell line that produces identical (monoclonal) antibodies.
Related Question 5
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.