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Test: GRE Subject Test: Biochemistry, Cell, and Molecular Biology
Two students receive 1 microliter of plasmid DNA that expressed beta-lactamase under a constitutive promoter, and green fluorescent protein (eGFP) under an arabinose inducible promoter.
The students decide to heat shock transform the entire volume of plasmid DNA into chemically competent bacterial cells to ensure that they have enough replicated plasmid for future experiments. The students also transform the same volume of sterile water as a control. They plate their transformations on the following plates:
1. Nutrient agar
2. Nutrient agar plus ampicillin
3. Nutrient agar plus ampicillin and arabinose
The next day, the students observe a lawn of bacteria on each plate for bacterica transformed with the plasmid, with only 1/10 of the bacteria glowing green on plate 3. Additionally, they observe a lawn of bacteria on each plate for the control condition.
| 1. | Which is most likely the cause of their results? |
The plasmid does not confer ampicillin resistance to the bacteria
There is not enough information given to interpret the results
The ampicillin in the nutrient agar plates expired
The heat shock transformation did not successfully introduce plasmid DNA into the bacteria
The plasmid mutated and now expresses eGFP constitutively
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