A control experiment grows bacteria for five rounds on plates without antibiotic, then tests their MIC. The control populations show MIC similar to the ancestor. The selected populations show 64-fold increases in MIC.
What does the unselected control rule out?
- Acheck_circle
The hypothesis that random drift or growth alone increased resistance
- B
The hypothesis that bacteria are clonal
- C
The hypothesis that antibiotics kill bacteria
- D
The hypothesis that mutations occur during growth
Explanation
By showing that growth alone (without selection pressure) does not raise MIC, the control rules out drift or growth-related artifacts. The MIC increase in the selected lines is therefore attributable to selection.