MCAT Math Question 16: Answer and Explanation
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Question: 16
1. An experimenter is attempting to investigate the effect of a new antibiotic on E. coli. He plates cells and administers one milliliter of the antibiotic. Which of the following is an appropriate negative control in this experiment?
- A. A plate with no cells that was coated with one milliliter of antibiotic.
- B. A plate with E. coli and no additional treatment.
- C. A plate with E. coli and one milliliter of isotonic saline.
- D. A plate of epithelial cells treated with one milliliter of antibiotic.
Correct Answer: C
Explanation:
The purpose of a control is to keep the conditions of two experiments as close as possible to establish causality. In this case, the one milliliter volume addition might have impacted the growth of E. coli; thus, we must control for this by administering an equal volume of a theoretically inert compound to a plate of E. coli.