A bacterium is said to be transformed when:
A) It has taken up foreign DNA directly from the environment
B) It undergoes gene mutations caused by mutagens
C) It is engulfed by a macrophage through phagocytosis
D) It is able to grow under anaerobic conditions
E) It has a cell wall similar to that of plant cells
IMAT 2026 · Question 19
Q19 - Prokaryotic DNA
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The correct answer is A) It has taken up foreign DNA directly from the environment.
Bacteria can acquire new genes in three ways: transformation (taking up free DNA from the surroundings), conjugation (through a pilus, from another bacterium) and transduction (carried by a virus). In Griffith’s classic experiment, harmless bacteria became virulent after taking up DNA from dead virulent bacteria.
A) Correct: Taking up free DNA from the environment is the definition of transformation.
B) Incorrect: A mutation changes DNA the bacterium already has. No foreign DNA is acquired.
C) Incorrect: Phagocytosis by a macrophage destroys the bacterium. It is part of the immune response.
D) Incorrect: Growing without oxygen is a metabolic feature (anaerobic or facultative bacteria), not transformation.
E) Incorrect: Bacterial walls are made of peptidoglycan, plant walls of cellulose. Either way, it has nothing to do with transformation.
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