LSAT 104 – Section 4 – Question 24

LSAT 104 - Section 4 - Question 24

December 1998

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Question
QuickView		 Type Tags Answer
Choices		 Curve Question
Difficulty		 Psg/Game/S
Difficulty		 Explanation
PT104 S4 Q24
+LR
Argument part +AP
Causal Reasoning +CausR
A
5%
160
B
3%
162
C
76%
170
D
5%
163
E
10%
165
149
158
167
 +Harder 147.438 +SubsectionMedium

Scientists, puzzled about the development of penicillin-resistant bacteria in patients who had not been taking penicillin, believe they have found an explanation. The relevant group of patients have dental fillings made of mercury-containing amalgam, and the bacteria the patients develop are immune to mercury poisoning. Scientists have concluded that the genes causing resistance to penicillin are closely bundled on the chromosomes of bacteria with the gene that produces immunity to mercury poisoning. Exposure to the mercury kills off bacteria that lack the relevant immunity gene, and leaves room for those that possess both the mercury-immunity gene and the penicillin-resistance gene to flourish.

Summarize Argument: Causal Explanation
Scientists are super confused about penicillin-resistant bacteria in patients who don’t use penicillin. (Their confusion implies that resistance normally only occurs when people use penicillin.) However, the scientists have a solution: the bacteria are being naturally selected by mercury instead. This is supported by the bacteria being immune to mercury poisoning. We also learn that mercury-resistance genes are related to penicillin-resistance genes. Finally, the patients in question have mercury in their cavity fillings, giving us a source of mercury exposure.

Identify Argument Part
The assumption that some patients who take penicillin develop bacteria with an immunity to penicillin is part of what makes penicillin resistance without exposure to penicillin confusing.

A
It is a hypothesis that is taken by the scientists to be conclusively proven by the findings described in the passage.
Nothing in the argument is taken to prove a hypothesis that penicillin use can lead to penicillin-resistant bacteria. It’s also not a hypothesis at all, it’s an assumption that’s taken for granted and treated as a fact.
B
It is a generalization that, if true, rules out the possibility that some people who do not take penicillin develop bacteria resistant to it.
The scientists do not believe that penicillin leading to resistance would mean that penicillin is the only way to create resistance. The entire argument is based on the belief that some other factor could lead to resistance, and the scientists just have to figure out what.
C
It is a point that, 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.
This is exactly what the assumption about penicillin causing resistance does in the argument. It’s the reason that resistance in the absence of penicillin is confusing, leading to the scientists doing this research in the first place.
D
It is the tentative conclusion of previous research that appears to be falsified by the scientists’ discovery of the mechanism by which bacteria become resistant to mercury poisoning.
Nothing in this argument falsifies anything else. Mercury causing penicillin resistance doesn’t mean that penicillin can’t also cause penicillin resistance. Both are treated as compatible.
E
It is a generalization assumed by the scientists to conclusively prove that the explanation of their problem case must involve reference to the genetic makeup of the penicillin-resistant bacteria.
This is a trap; complicated does not mean correct. The assumption that penicillin can cause resistance doesn’t prove anything. It’s context for why the scientists are confused to start with.

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LSAT PrepTest 104 Explanations

Section 1 - Logical Reasoning

Section 2 - Reading Comprehension

Section 3 - Reading Comprehension

Section 4 - Logical Reasoning

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