Some bacteria are able to grow in Streptomycin containing medium due to -
A
Natural selection
B
Induced mutation
C
Reproductive isolation
D
Genetic drift
The answer is A.
Solution
In a large bacterial population, a few cells already carry random (spontaneous) mutations that make them resistant to streptomycin. These mutations are pre-existing; the antibiotic does not cause them (Lederberg's replica plating experiment). When the bacteria are grown on streptomycin medium, the sensitive cells die and only the resistant ones survive and multiply. This is natural selection, with the antibiotic acting as the selecting agent. So the bacteria grow in streptomycin medium due to natural selection.
ConceptSelection of resistant bacteria
Evolution in past papers
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