Biology · Evolutionary Genetics
In a polluted aquatic environment, bacteria are chronically exposed to low concentrations of antibiotics. To determine whether antibiotic resistance arises through induced mutation or random mutation followed by selection, an ecologist performs a fluctuation test similar to that of Luria and Delbrück (1943) using replicate bacterial cultures. Which one of the following outcomes best supports the conclusion that resistance arises by random mutation prior to selection?
Verified Solution4 OptionsUpdated: October 2026👁️1 View
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- 1The number of resistant colonies increases predictably and proportionally with exposure time in every replicate culture.
- 2Resistant colonies appear only after antibiotic addition.
- 3Different replicate cultures show large fluctuations in the number of resistant colonies, even though each was treated identically.✓
- 4Each replicate culture yields nearly the same number of resistant colonies after exposure to the antibiotic.
Correct answer
Different replicate cultures show large fluctuations in the number of resistant colonies, even though each was treated identically.
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