LSAT 70, Reading Comprehension, Q7

DISCUSSION: Scientists haven’t proven that prions cause CJD. They’ve just noticed a correlation. Prions replicate, and CJD progresses. This isn’t extremely clear in the passage, since the third paragraph indicates that prions are definitely the cause. But paragraphs 2 and 4 make clear that there’s still some doubt about whether prions actually cause CJD. See lines 48-52 (They say the experiments “supported the conclusion”….not proved), and lines 12-14 (They say that the “assumption has been challenged”….not disproven).

So there may only be a correlation between prions and CJD. We can weaken the idea that prions cause CJD by showing that prions aren’t harmful, or that something else causes CJD.

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1. Tempting, but many diseases share the same symptoms. CJD’s symptoms cause loss of mental acuity and insomnia. That describes two of the symptoms of the common cold!
   Either a disease is CJD or it isn’t. To be right, this answer would have had to link the viral infection to patients actually diagnosed with CJD, or with those experiencing a disease so similar that it could also be classed as a neurodegenerative disease.
2. If the therapies cured CJD, then this would be the right answer. But the therapies could be totally ineffective, so the fact that the therapies don’t block prion reactions doesn’t mean prion reactions aren’t the cause of CJD. The mere fact that we use remedies doesn’t prove that the remedies work, unfortunately. The therapies might just treat secondary effects or relieve pain.
3. This doesn’t show that prions don’t cause CJD. This answer just shows that prions cause even more problems. 2
4. The stimulus never mentioned whether malfunctioning prions were hereditary. So this answer tells us nothing about prions.
5. CORRECT. Prions aren’t bacteria. So if an anti-bacterial drug reverses CJD, then it sounds like bacteria are the cause, not prions. This answer is especially significant since up until now CJD was fatal – we had no way to reverse it (line 45).

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