Question

The spontaneous, and induced mutations in bacteria can be distinguished by

• A. fluctuation test
• B. replica plating
• C. disc diffusion test
• D. use-dilution test

Hint:

Remember: Fluctuation test and replica plating are the classical experiments proving that mutations are spontaneous, not induced by the environment.

Answer 1

The Correct Option is A, B

Step 1: Fluctuation test. Luria–Delbrück fluctuation test distinguishes between spontaneous vs induced mutations by showing that mutations occur randomly prior to selection, not as a directed response. Hence, (A) is correct.
Step 2: Replica plating. Lederberg’s replica plating experiment demonstrated that resistant mutants pre-exist in the population (spontaneous) rather than being induced by the selective agent. Hence, (B) is correct.
Step 3: Other tests. (C) Disc diffusion test: used for antibiotic sensitivity, not mutation distinction.
(D) Use-dilution test: used for disinfectant evaluation.
Therefore, the correct answers are (A) and (B).