Which one of the following, if true, would most undermine the claim that prions cause CJD?

Sydney on September 9, 2019


Can you please explain why E is the correct answer and the others are wrong. Thanks!


Irina on September 10, 2019


The passage tells us that prions are different from all other pathogens - bacteria, fungi, and parasites in that it lacks genetic material in their cellular structure (lines 5-11, 19-24). The fact that antibacterial drug - aimed at a pathogen with genetic material - is proving to be effective in reversing the onset of CJD per (E) would suggest that CJD is bacterial in nature and thus weaken the claim that it is caused by prions.

Let's briefly review the incorrect answer choices:

(A) Several symptoms resembling those of CJD have been experienced by patients known to have a viral infection.

Incorrect. It is irrelevant that a viral infection has similar symptoms to CJD, many conditions may have similar symptoms but entirely different causes. We are only interested in whether prions cause CJD not the cause of another viral infection.

(B) None of the therapies currently available for treating neurological diseases is designed to block the chain reaction by which prions reproduce.

Incorrect. There are a couple of issues with this answer choice - first of all, it is too broad, neurological diseases encompass a wide variety of diseases not only CJD, and second - the passage explicitly tells us that there is no therapy available (lines 43-35) as the exact mechanisms by which prions reproduced are not fully understood yet.

(C) Research undertaken subsequent to the studies on CJD has linked prions to degenerative conditions not affecting the brain or the central nervous system.

Incorrect. This fact merely tells us that prions can cause damage to other organs, not that they cannot cause CJD.

(D) Epidemiological studies carried out on a large population have failed to show any hereditary predisposition to CJD.

Incorrect. The passage never says that prion transformations are somehow hereditary, rather prions normally exist in many tissues, and the mechanism of abnormal conversion is not yet fully understood.

Let me know if this helps and if you have any further questions.

Andrew on April 29, 2021

Hi, how do we know that the antibacterial drug mentioned in answer choice E is aimed at a pathogen with genetic material?