LSAT Explanation PT 27, S4, Q24: Scientists, puzzled about the development of

LSAT Question Stem

Which one of the following most accurately characterizes the role played in the passage by the unstated assumption that some patients who take penicillin develop bacteria with an immunity to penicillin? 

Logical Reasoning Question Type

This is an Argument Part question. 

Correct Answer

The correct answer to this question is C. 

LSAT Question Complete Explanation

Let's first analyze the argument in the passage. The argument focuses on the puzzling development of penicillin-resistant bacteria in patients who had not been taking penicillin. Scientists believe they have found an explanation for this phenomenon: these patients have dental fillings made of mercury-containing amalgam, and the bacteria they develop are immune to mercury poisoning. The scientists conclude that the genes causing resistance to penicillin are closely bundled with the gene that produces immunity to mercury poisoning on the chromosomes of bacteria. When exposed to mercury, bacteria lacking the immunity gene die, leaving room for those with both the mercury-immunity gene and the penicillin-resistance gene to flourish. The structure of the argument can be summarized as follows:

- Premise: Some patients who had not been taking penicillin develop penicillin-resistant bacteria.

- Premise: These patients have mercury-containing dental fillings.

- Premise: The bacteria they develop are immune to mercury poisoning.

- Conclusion: The genes causing resistance to penicillin are bundled with the gene that produces immunity to mercury poisoning on the chromosomes of bacteria.

Now, let's consider the question type and what it's asking us to do. This is an Argument Part question, which asks us to identify the role played by an unstated assumption in the passage. The unstated assumption is that some patients who take penicillin develop bacteria with an immunity to penicillin.

Let's examine each answer choice in detail:

a) This answer choice is incorrect because the unstated assumption is not a hypothesis that is proven by the findings in the passage. It is, rather, a point that helps generate the problem that prompted the research.

b) This answer choice is also incorrect because the unstated assumption is not a generalization that rules out the possibility that some people who do not take penicillin develop bacteria resistant to it. In fact, the passage discusses this very phenomenon.

c) This is the correct answer. The unstated assumption, when combined with the fact that some patients who do not take penicillin develop penicillin-resistant bacteria, generates the problem that prompted the research described in the passage. In other words, it creates the puzzle that the scientists are trying to solve.

d) This answer choice is incorrect because the unstated assumption is not the tentative conclusion of previous research that is falsified by the scientists' discovery. It is, instead, a point that helps generate the problem that prompted the research.

e) This answer choice is incorrect because the unstated assumption is not a generalization that conclusively proves that the explanation of the problem must involve reference to the genetic makeup of the penicillin-resistant bacteria. The assumption helps generate the problem, but it does not determine the explanation.

In summary, the correct answer is C, as it accurately characterizes the role played by the unstated assumption in the passage. The assumption, in conjunction with the fact that some patients who do not take penicillin develop penicillin-resistant bacteria, generates the problem that prompted the research described in the passage.