Selected MCQ

Current Question
In biological membranes, unsaturated fatty acid chains cause which of the following effects on membrane fluidity?
  • A. Increase fluidity by preventing tight packing of phospholipids
  • B. Decrease fluidity by allowing closer packing of phospholipids
  • C. No effect on fluidity because head groups determine packing
  • D. Cause the membrane to become rigid at high temperature
Correct Answer: A
Explanation:
Cis double bonds in unsaturated fatty acids introduce kinks that prevent phospholipids from packing tightly, thereby increasing membrane fluidity.
Related Question 1
Which of the following best describes polygenic inheritance?
  • A. One gene affects multiple traits (e.g., pleiotropy)
  • B. Many genes contribute to one trait (e.g., skin color)
  • C. A trait determined by genes only on the X chromosome
  • D. Inheritance of mitochondrial DNA
Correct Answer: B
Explanation:
Polygenic inheritance means multiple genes (often with additive effects) determine a single phenotype, such as height or skin color, producing continuous variation.
Related Question 2
Which of the following is NOT typically controlled during industrial fermentation in a bioreactor?
  • A. Temperature
  • B. pH
  • C. Oxygen concentration
  • D. DNA sequence of the microorganism
Correct Answer: D
Explanation:
A, B, and C (temperature, pH, oxygen) are critical parameters controlled in fermentation. The chosen strain fixes the DNA sequence and is not a controlled parameter during the run.
Related Question 3
Which of the following techniques compares short tandem repeat (STR) regions among individuals for identification?
  • A. Western blot
  • B. DNA microarray
  • C. DNA fingerprinting
  • D. Northern blot
Correct Answer: C
Explanation:
DNA fingerprinting analyzes highly polymorphic regions, especially STRs, to distinguish individuals (used in forensics and paternity testing).
Related Question 4
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 5
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.