An organism is considered to have an infection when a disease-causing

Question

An organism is considered to have an infection
when a disease-causing agent, called a pathogen,
establishes a viable presence in the organism. This can
occur only if the pathogenic agent is able to reproduce
  (5)   itself in the host organism. The only agents believed
until recently to be responsible for infections—viruses,
bacteria, fungi, and parasites—reproduce and regulate
their other life processes by means of genetic material,
composed of nucleic acid (DNA or RNA). It was thus
  (10)   widely assumed that all pathogens contain such
genetic material in their cellular structure.

This assumption has been challenged, however,
by scientists seeking to identify the pathogen that
causes Creutzfeldt-Jakob disease (CJD), a degenerative
  (15)   form of dementia in humans. CJD causes the brain to
become riddled with tiny holes, like a sponge (evidence
of extensive nerve cell death). Its symptoms include
impaired muscle control, loss of mental acuity, memory
loss, and chronic insomnia. Extensive experiments
  (20)   aimed at identifying the pathogen responsible for CJD
have led surprisingly to the isolation of a disease agent
lacking nucleic acid and consisting mainly, if not
exclusively, of protein. Researchers coined the term
“prion” for this new type of protein pathogen.

(25)   Upon further study, scientists discovered that
prions normally exist as harmless cellular proteins in
many of the body’s tissues, including white blood cells
and nerve cells in the brain; however, they possess the
capability of converting their structures into a
  (30)   dangerous abnormal shape. Prions exhibiting this
abnormal conformation were found to have infectious
properties and the ability to reproduce themselves in
an unexpected way, by initiating a chain reaction that
induces normally shaped prions to transform
  (35)   themselves on contact, one after another, into the
abnormal, pathogenic conformation. This cascade of
transformations produces a plaque, consisting of
thread-like structures, that collects in the brain and
ultimately destroys nerve cells. Because prions, unlike
  (40)   other pathogens, occur naturally in the body as
proteins, the body does not produce an immune
response when they are present. And in the absence
of any effective therapy for preventing the cascade
process by which affected prions reproduce
  (45)   themselves, CJD is inevitably fatal, though there are
wide variations in pre-symptomatic incubation times
and in how aggressively the disease progresses.

Although the discovery of the link between prions
and CJD was initially received with great skepticism
  (50)   in the scientific community, subsequent research has
supported the conclusion that prions are an entirely
new class of infectious pathogens. Furthermore, it is
now believed that a similar process of protein
malformation may be involved in other, more
  (55)   common degenerative neurological conditions such
as Alzheimer’s disease and Parkinson’s disease.
This possibility has yet to be fully explored, however,
and the exact mechanisms by which prions reproduce
themselves and cause cellular destruction have yet to
  (60)   be completely understood.    1 
 1. Which one of the following most accurately expresses the main point of the passage?

(A) Although most organisms are known to produce several kinds of proteins, the mechanism by which isolated protein molecules such as prions reproduce themselves is not yet known in detail.
(B) Research into the cause of CJD has uncovered a deadly class of protein pathogens uniquely capable of reproducing themselves without genetic material.
(C) Recent research suggests that prions may be responsible not only for CJD, but for most other degenerative neurological conditions as well.
(D) The assertion that prions cause CJD has been received with great skepticism in the scientific community because it undermines a firmly entrenched view about the nature of pathogens.
(E) Even though prions contain no genetic material, it has become clear that they are somehow capable of reproducing themselves.

2 
 2. Which one of the following is most strongly supported by the passage?

(A) Understanding the cause of CJD has required scientists to reconsider their traditional beliefs about the causes of infection.
(B) CJD is contagious, though not highly so.
(C) The prevention of CJD would be most efficiently achieved by the prevention of certain genetic abnormalities.
(D) Although patients with CJD exhibit different incubation times, the disease progresses at about the same rate in all patients once symptoms are manifested.
(E) The prion theory of infection has weak support within the scientific community.

3 
 3. If the hypothesis that CJD is caused by prions is correct, finding the answer to which one of the following questions would tend most to help a physician in deciding whether a patient has CJD?

(A) Has the patient suffered a severe blow to the skull recently?
(B) Does the patient experience occasional bouts of insomnia?
(C) Has the patient been exposed to any forms of radiation that have a known tendency to cause certain kinds of genetic damage?
(D) Has any member of the patient’s immediate family ever had a brain disease? 
(E) Does the patient’s brain tissue exhibit the presence of any abnormal thread-like structures?

4 
 4. Which one of the following is most strongly supported by the passage?

(A) The only way in which CJD can be transmitted is through the injection of abnormally shaped prions from an infected individual into an uninfected individual.
(B) Most infectious diseases previously thought to be caused by other pathogens are now thought to bencaused by prions.
(C) If they were unable to reproduce themselves, abnormally shaped prions would not cause CJD.
(D) Alzheimer’s disease and Parkinson’s disease are caused by different conformations of the same prion pathogen that causes CJD.
(E) Prion diseases generally progress more aggressively than diseases caused by other known pathogens.

5 
 5. It can be inferred from the passage that the author would be LEAST likely to agree with which one of the following?

(A) The presence of certain abnormally shaped prions in brain tissue is a sign of neurological disease.
(B) Some patients currently infected with CJD will recover from the disease.
(C) Prions do not require nucleic acid for their reproduction.
(D) The body has no natural defense against CJD.
(E) Scientists have only a partial understanding of the mechanism by which prions reproduce

6 
 6. Given the manner in which the term “pathogen” is used in the passage, and assuming that the prion theory of infection is correct, which one of the following statements must be false?

(A) Nothing that lacks nucleic acid is a pathogen.
(B) Prions are a relatively newly discovered type of pathogen.
(C) All pathogens can cause infection.
(D) Pathogens contribute in some manner to the occurrence of CJD.
(E) There are other pathogens besides viruses, bacteria, fungi, and parasites.

7 
 7. Which one of the following, if true, would most undermine the claim that prions cause CJD?

(A) Several symptoms closely resembling those of CJD have been experienced by patients known to have a specific viral infection.
(B) None of the therapies currently available for treating neurological diseases is designed to block the chain reaction by which abnormal prions are believed to reproduce.
(C) Research undertaken subsequent to the studies on CJD has linked prions to degenerative conditions not affecting the brain or the central nervous system.
(D) Epidemiological studies carried out on a large population have failed to show any hereditary predisposition to CJD.
(E) A newly developed antibacterial drug currently undergoing clinical trials is proving to be effective in reversing the onset of CJD.

Sajjad1994 · Accepted Answer

Explanation

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

Explanation

The credited response will make the claim that prions cause CJD less likely to be true.

A. No.  This answer merely suggests that CJD shares symptoms with another infection but does not address the connection between prions and CJD.

B. No.  This is consistent with the passage’s claim that there is no effective therapy for preventing the prion chain reaction.

C. No.  The fact that prions are linked to other degenerative conditions makes it more likely that it could be linked to CJD, even though the other conditions affect different parts of the body.

D. No.  The passage makes no claims about hereditary predisposition to CJD.

E.  Yes.   If an antibacterial drug is effective against CJD, it is likely that CJD is caused by bacteria rather than prions.

Answer: E

GMATNinja · Answer

Question 7 
 
Question 7 asks us which answer choice, if true, would  most undermine  the claim that prions cause CJD. So, we're not looking for something that PROVES that prions don't cause CJD -- the bar is much lower than that. We're just looking for the option that undermines the claim more than the other options do.

Here's (E):

(E) tells us that an antibacterial drug is proving to be effective against CJD. This points the finger at bacteria instead of prions, so it undermines the claim that prions cause CJD.

As to the issues that you brought up: it really wouldn't make sense to do a clinical trial of a drug and ONLY have a placebo group. That wouldn't be a trial of the drug at all, so it just doesn't apply to the info in (E).

On the other hand,  could  there be something else in the drug that happens to impact prions? Sure, that's possible. But remember that we're just trying to undermine the prion theory, and we don't have to  prove  that it's totally wrong.

On balance, (E) definitely undermines the theory by introducing a lot of doubt about whether CJD is actually caused by bacteria. That doubt is enough to choose (E), even if you can think of edge cases in which more info could weaken the force of (E).

I hope that helps!

Sajjad1994 · Answer

Explanation

4. Which one of the following is most strongly supported by the passage?

Explanation

The correct answer will be the statement that is best supported by evidence within the passage text.

A. No.  The passage does not discuss how individuals are infected.

B. No.  This answer choice is too strong. The passage mentions that two other diseases may be linked to prions, but says that the connection has yet to be fully explored. Even if it were fully explored, there is not enough to support “most.”

C. Yes.  In the third paragraph, the passage states that the chain reaction of prion transformation causes the plaque that destroys nerve cells.

D. No.  This answer choice is too strong. The passage states that the possibility that Alzheimer’s and Parkinson’s are caused by prions has yet to be fully explored or understood.

E. No.  The passage does not compare the speed of progression of CJD with that of other diseases.

Answer: C

Sajjad1994 · Answer

Explanation

6. Given the manner in which the term “pathogen” is used in the passage, and assuming that the prion theory of infection is correct, which one of the following statements must be false?

Explanation

The four incorrect answers will be things that could be true, and the credited response will conflict with statements in the passage.

A. Yes.  In the end of the second paragraph, the passage discusses that prions are pathogens that lack nucleic acid.

B. No.  This is compatible with the passage. The passage calls prions a new type of pathogen at the end of the second paragraph.

C. No.  This is compatible with the passage. In the first paragraph, the passage defines pathogens as disease-causing agents and does not exclude the possibility that all pathogens are infectious.

D. No.  This is compatible with the passage. The fourth paragraph discusses the link between prions, a type of pathogen, and CJD.

E. No.  This is compatible with the passage. The passage argues that prions are a type of pathogen as well.

Answer: A

HarshaBujji · Answer

Para Summary :

The passage describes how infections occur when pathogens, such as viruses, bacteria, fungi, and parasites, establish themselves in an organism and reproduce using genetic material. However, researchers have discovered a new type of protein pathogen, called a prion, which causes Creutzfeldt-Jakob disease (CJD) and lacks nucleic acid. Prions can convert their structures into an abnormal shape, inducing other normal prions to transform, resulting in a cascade of transformations that produce a plaque in the brain, destroying nerve cells. Prions are an entirely new class of infectious pathogens, and a similar process may be involved in other neurological conditions such as Alzheimer’s and Parkinson’s diseases.

Main Idea of the passage :

To highlight the discovery of a new type of protein pathogen.

anish777 · Answer

I have gone through one of the explanations provided for answer 7 but I am not convinced.
Here option C clearly mentions that the degenerative actions do not affect the brain. From the passage, we get the idea that the CJD is caused in the brain. So, if prion has no degenerative actions in the brain, how can it be responsible for CJD ?
I understand option E looks more logical, but we cannot rule out option C for the reason described in the previous explanation.

Nielgmat · Answer

Hi Anish,
This is what Option C says..
(C) Research undertaken subsequent to the studies on CJD has  linked prions to degenerative conditions not affecting the brain or the central nervous system.

It means that prions are linked to degenerative conditions  other than those affecting the brain.. 
These degenerative conditions can be in addition to CJD. The option does not say that prions do not cause CJD.
we need an option that 'would  most undermine  the claim that prions cause CJD?'

Hence, between E and C, E is better suited.
Hope it helps..

Oppenheimer1945 · Answer

Why is E correct? This anti-bacterial drug might have a compositional chemical that retards the CJD? What if the trials actually not the real drug and is a palcebo?

Sajjad1994 · Answer

Explanation

1. Which one of the following most accurately expresses the main point of the passage?

Explanation

Use your Bottom Line of the passage to help you to evaluate the choices. The correct answer will discuss the role of prions in CJD.

A. No.  This choice is too narrow and does not mention CJD.

B.  Yes.   This is an accurate paraphrase of the Bottom Line.

C. No.  This answer choice is extreme. The passage suggests that prions may be involved in other degenerative diseases, but it says that the possibility has yet to be fully explored.

D. No.  This answer choice is too narrow. The passage notes that the connection was initially received with skepticism, but additional research supports the link between prions and CJD.

E. No.  This answer choice is too narrow and does not mention CJD.

Answer: B

VerbalBot · Answer

Automated notice from GMAT Club VerbalBot: 

A member just gave Kudos to this thread, showing it’s still useful. I’ve bumped it to the top so more people can benefit. Feel free to add your own questions or solutions.

 This post was generated automatically.

An organism is considered to have an infection when a disease-causing

Prep Toolkit

Top 5 GMAT Debrief Videos

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards

GMAT Reading Comprehension (RC) Questions

An organism is considered to have an infection when a disease-causing

Prep Toolkit

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards