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The single-celled parasite known as Toxoplasma gondii infects more

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The single-celled parasite known as Toxoplasma gondii infects more  [#permalink]

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New post Updated on: 25 Jul 2018, 04:37
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The single-celled parasite known as Toxoplasma gondii infects more than half of the world's human population without creating any noticeable symptoms. Once inside the human body, Toxoplasma rapidly spreads to the heart and other organs. It can even penetrate the tight barrier that normally protects the brain from most pathogens. Yet, the blood of infected persons carries very few free-floating Toxoplasma cells. Scientists have long been puzzled by this ability of Toxoplasma to parasitize the human body without triggering an immune response and without an appreciable presence in the bloodstream. Recent research, however, has shed light on the ways in which Toxoplasma achieves its remarkable infiltration of the human body.

Though there are few individual Toxoplasma cells coursing freely in the blood of an infected person, scientists have discovered that the parasite is quite common in certain cells, known as dendritic cells, involved in the human immune system. Dendritic cells are found in the digestive tract and frequently come into contact with the various pathogens that enter the human body through food and water. When the dendritic cells encounter pathogens, they travel to lymph nodes and relay this information to other immune cells that then take action against the reported pathogen. Scientists have found, however, that Toxoplasma is capable of hijacking dendritic cells, forcing them from their usual activity and using them as a form of transportation to infect the human body quickly. Without this transport mechanism, Toxoplasma could not reach the better-protected areas of the body.

Toxoplasma invades the human body through consumption of the undercooked meat of infected animals, primarily pigs and chickens. Other animals, such as cats, can become infected as well. In fact, cats are a necessary component in the reproductive cycle of Toxoplasma, since the animal's intestines are the parasite's sole breeding ground. Toxoplasma creates egg-like cysts, known as oocysts, in the cats' intestines. These oocysts are shed in the cats' droppings and contaminate ground water and soil, eventually finding their way into the food chain. Because Toxoplasma must somehow find its way into a new host cat in order to reproduce, it cannot kill its current host. Instead, it waits for the host, usually a small rodent, to be eaten by a cat, thus providing Toxoplasma the opportunity to reproduce.




1. According to the passage, all of the following are true of Toxoplasma gondii EXCEPT

(A) it can contaminate ground water
(B) it enters the human body through the food chain
(C) it can alter the usual behavior of human cells
(D) the human body is incapable of detecting it
(E) it must find a host cat in order to reproduce



2. It can be inferred from the passage that which of the following statements is true of dendritic cells in the human body?

(A) They are produced by the lymphatic system.
(B) They are more numerous in the digestive tract than in any other part of the human body.
(C) Most dendritic cells of persons infected with Toxoplasma carry the parasite.
(D) They are the only cells capable of being infected by Toxoplasma.
(E) They are able to penetrate the membranes surrounding the brain.



3. Which of the following is the most likely outcome for Toxoplasma cells that invade the human body?

(A) They will be destroyed by the immune system.
(B) They will collect in the lymphatic system.
(C) They will not reproduce.
(D) They will be detected after several weeks.
(E) They will be destroyed by other pathogens in the bloodstream.



4. The second paragraph performs which of the following functions in the passage?

(A) It describes a paradox that scientists were unable to resolve for some time.
(B) It explains the effectiveness of a lethal biological pathogen.
(C) It describes the mechanism by which a biological event occurs in humans.
(D) It demonstrates how the infectious agent reproduces itself.
(E) It introduces information that is essential to understanding the role of Toxoplasma in human development.



5. The author mentions “pigs and chickens” in the final paragraph in order to

(A) provide specific examples of animals that can carry Toxoplasma
(B) provide specific examples of animals that are often eaten by cats
(C) provide specific examples of other animals whose dendritic cells are exploited by Toxoplasma
(D) provide specific examples of animals in which Toxoplasma can breed
(E) provide specific examples of animals that are immune to Toxoplasma


Originally posted by nikhilpoddar on 08 Sep 2009, 03:49.
Last edited by Bunuel on 25 Jul 2018, 04:37, edited 8 times in total.
Edited the OAs.
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Re: The single-celled parasite known as Toxoplasma gondii infects more  [#permalink]

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New post Updated on: 04 Sep 2016, 00:02
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Part of New Project-->[url=http://gmatclub.com/forum/new-project-reading-comprehension-review-practice-195318.html]Reading Comprehension!!- Review/ Practice[/url]


The single-celled parasite known as Toxoplasma gondii infects more than half of the world's human population without creating any noticeable symptoms. Once inside the human body, Toxoplasma rapidly spreads to the heart and other organs. It can even penetrate the tight barrier that normally protects the brain from most pathogens. Yet, the blood of infected persons carries very few free-floating Toxoplasma cells. Scientists have long been puzzled by this ability of Toxoplasma to parasitize the human body without triggering an immune response and without an appreciable presence in the bloodstream. Recent research, however, has shed light on the ways in which Toxoplasma achieves its remarkable infiltration of the human body.

Though there are few individual Toxoplasma cells coursing freely in the blood of an infected person, scientists have discovered that the parasite is quite common in certain cells, known as dendritic cells, involved in the human immune system. Dendritic cells are found in the digestive tract and frequently come into contact with the various pathogens that enter the human body through food and water. When the dendritic cells encounter pathogens, they travel to lymph nodes and relay this information to other immune cells that then take action against the reported pathogen. Scientists have found, however, that Toxoplasma is capable of hijacking dendritic cells, forcing them from their usual activity and using them as a form of transportation to infect the human body quickly. Without this transport mechanism, Toxoplasma could not reach the better-protected areas of the body.

Toxoplasma invades the human body through consumption of the undercooked meat of infected animals, primarily pigs and chickens. Other animals, such as cats, can become infected as well. In fact, cats are a necessary component in the reproductive cycle of Toxoplasma, since the animal's intestines are the parasite's sole breeding ground. Toxoplasma creates egg-like cysts, known as oocysts, in the cats' intestines. These oocysts are shed in the cats' droppings and contaminate ground water and soil, eventually finding their way into the food chain. Because Toxoplasma must somehow find its way into a new host cat in order to reproduce, it cannot kill its current host. Instead, it waits for the host, usually a small rodent, to be eaten by a cat, thus providing Toxoplasma the opportunity to reproduce.



1. The second paragraph performs which of the following functions in the passage?

A. It describes a paradox that scientists were unable to resolve for some time.
B. It explains the effectiveness of a lethal biological pathogen.
C. It describes the mechanism by which a biological event occurs in humans.
D. It demonstrates how an infectious agent enters the human body.
E. It introduces information that is essential to understanding the role of Toxoplasma in human development.



1 (New).The second paragraph performs which of the following functions in the passage?
A. It summarizes the research that remains to be done regarding Toxoplasma.
B. It presents a recommendation based on the new understanding of Toxoplasma.
C. It describes the mechanism by which Toxoplasma is able to parasitize the human body.
D. It introduces information that is essential to understanding the role of Toxoplasma in human development.
E. It discusses an outdated scientific model that has been discredited and offers a new model in its place.



2. Which of the following is the most likely outcome for Toxoplasma cells that invade the human body?

A. They will be destroyed by the immune system.
B. They will collect in the lymphatic system.
C. They will not reproduce.
D. They will be detected after several weeks.
E. They will be destroyed by other pathogens in the bloodstream.



3. According to the passage, all of the following are true of Toxoplasma gondii EXCEPT

A. it can contaminate ground water
B. it enters the human body through the food chain
C. it can alter the usual behavior of human cells
D. the human body is incapable of detecting it
E. it must find a host cat in order to reproduce



4.
It can be inferred from the passage that which of the following statements is true of dendritic cells in the human body?
A. They are produced by the lymphatic system.
B. They are more numerous in the digestive tract than in any other part of the human body.
C. Most dendritic cells of persons infected with Toxoplasma carry the parasite.
D.They are the only cells capable of being infected by Toxoplasma.
E. They are able to penetrate the membranes surrounding the brain.



5.
The author mentions “pigs and chickens” in the final paragraph in order to
A. provide specific examples of animals that can carry Toxoplasma
B.provide specific examples of animals that are often eaten by cats
C. provide specific examples of other animals whose dendritic cells are exploited by Toxoplasma
D. provide specific examples of animals in which Toxoplasma can breed
E. provide specific examples of animals that are immune to Toxoplasma



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Originally posted by Gnpth on 01 Apr 2015, 04:16.
Last edited by Skywalker18 on 04 Sep 2016, 00:02, edited 1 time in total.
Added fourth and fifth questions and a different variation of first question
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Re: The single-celled parasite known as Toxoplasma gondii infects more  [#permalink]

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New post 09 Sep 2009, 07:08
Good RC!
1. E ( must is too extreme even in the passage it has been mentioned that
Quote:
In fact, cats are a necessary component in the reproductive cycle of Toxoplasma
, it is necessary not a must condition)

2.E
(In first paragraph
Quote:
It can even penetrate the tight barrier that normally protects the brain from most pathogens

Please see the last line of the second paragraph
Quote:
Without this transport mechanism, Toxoplasma could not reach the better-protected areas of the body.
hence we can conclude that d-cells are able to penetrate protected areas such as brain)

3.D
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Re: The single-celled parasite known as Toxoplasma gondii infects more  [#permalink]

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New post 07 Dec 2012, 05:57
nikhilpoddar wrote:
anyone else ???


The second paragraph performs which of the following functions in the passage?
It describes a paradox that scientists were unable to resolve for some time.
It explains the effectiveness of a lethal biological pathogen.
It describes the mechanism by which a biological event occurs in humans.
It demonstrates how an infectious agent enters the human body.
It introduces information that is essential to understanding the role of Toxoplasma in human development.
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Re: The single-celled parasite known as Toxoplasma gondii infects more  [#permalink]

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New post 09 Dec 2012, 20:05
passage is not hard but question is hard. The hardness of answering questions come from the problem that we can not find the place to yield the answer. all questions do not show the relevant places. on real gmat we do not get this situation. only a few question do not show the relevant places.

I get all 3 wrong.
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New post 16 Dec 2012, 02:40
1
nikhilpoddar wrote:
OA
D
E
C


What is source of these passage?
How 'E' can be answer for second question no where its stated that dendritic cell can penetrate brain membrane
its Taxoplasma(mentioned in passage 1)
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New post 03 May 2014, 17:11
can some one please elaborate on the Ans.

1- D (how is it possible, Para 1 says it can can pass through human immune system and is detected much later due to the symptoms caused..)
Why is A wrong -- passage says the water is contaminated by cat droppings containing mould -- via soil and water(but the pathogen itself dosent goto soil to contaminate it)

2- E ( 2nd para never says that they are produced by lump nodes --they only travel towards lymp nodes when encountered by pathogens)
* B is clearly given in passage why not B? :-p

Any one can shed some light please.
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New post 06 May 2014, 05:22
Aristocrat wrote:
nikhilpoddar wrote:
OA
D
E
C


What is source of these passage?
How 'E' can be answer for second question no where its stated that dendritic cell can penetrate brain membrane
its Taxoplasma(mentioned in passage 1)



HEY,
first of all, this is inference question.....the answer choice will not be stated as it is in the passage , rather it will be distorted. For the E can be inferred
from the passage. Taxoplasma can penetrate human brain ( mentioned in the first paragraph)..but Taxoplasma can move to the body only by using Dendritic cell
( mentioned in the last line of 2nd paragraph).
SO dendritic cell can penetrate brain membrane.
hope it helps!!!!
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New post 23 Jun 2014, 14:12
Can someone please explain the first question.
"Scientists have long been puzzled by this ability of Toxoplasma to parasitize the human body without triggering an immune response and without an appreciable presence in the bloodstream."
So how can D be the correct answer?
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New post 18 Aug 2014, 00:42
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ronr34 wrote:
Can someone please explain the first question.
"Scientists have long been puzzled by this ability of Toxoplasma to parasitize the human body without triggering an immune response and without an appreciable presence in the bloodstream."
So how can D be the correct answer?


We are asked to determine which one of the five choices is NOT true of Toxoplasma, according to the passage. In other words, four of the five choices are stated in the passage and one choice is not. The choice that is not stated is the correct answer.

(A) The passage explicitly states that Toxoplasma can contaminate soil and water.

(B) The passage explicitly states that Toxoplasma enters the human body through contaminated food.

(C) The passage explicitly states that Toxoplasma alters the behavior of human dendritic cells.

(D) CORRECT. The word "incapable" in this answer choice is too strong; the passage does not state that the human body cannot detect Toxoplasma. Rather, it merely indicates that Toxoplasma does not trigger the body's immune system in the same way as other parasites. We have no information about the human body's ability to detect free-floating Toxoplasma cells.

(E) The passage explicitly states that Toxoplasma can breed in a host cat only.
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New post 18 Sep 2014, 04:19
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Its fair to consider D as one of the option due to its strong tone "incapable". However, Option C states that " it affects the usual behavior of human cells".
Going by the same yardstick, i think the option should be specific: human dendritic cells. But since it does not, why is this statement (C) loosely accepted and not "Incapable" one (D)

Also there are million types of cells in human body so the statement should be SPecific.
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New post 02 Apr 2015, 00:14
Hi

1. The second paragraph performs which of the following functions in the passage?

A. It describes a paradox that scientists were unable to resolve for some time.
B. It explains the effectiveness of a lethal biological pathogen.
C. It describes the mechanism by which a biological event occurs in humans.
D. It demonstrates how an infectious agent enters the human body.
E. It introduces information that is essential to understanding the role of Toxoplasma in human development.

Please explain. i choose A
Doubt b/t A and C
Explain plzz..!!
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New post 04 May 2015, 11:07
1
ssriva2 wrote:
dpo28 wrote:
Hi

1. The second paragraph performs which of the following functions in the passage?

A. It describes a paradox that scientists were unable to resolve for some time.
B. It explains the effectiveness of a lethal biological pathogen.
C. It describes the mechanism by which a biological event occurs in humans.
D. It demonstrates how an infectious agent enters the human body.
E. It introduces information that is essential to understanding the role of Toxoplasma in human development.

Please explain. i choose A
Doubt b/t A and C
Explain plzz..!!


even I choose A because of the last sentence in first para.Please explain this!


Hi

A: It can't be the appropriate choice because question is asking the role played by second para. If we think clearly, is second para all about describing how scientists resolve the paradox or is it describing a biological process mainly ?
Second para is mainly dealing with the description of how a process occurs.

If we look that way then only B and C seem appropriate. B is wrong because Toxoplasm is a parasite not a pathogen.
E is wrong because Toxoplasm don't play any role in human development rather they play role in destruction.
D is wrong because passage don't describe how it enters human body, the passage describes what it do inside the body (which can be done only after it has already been entered in the body)


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New post 14 May 2015, 20:17
4
Quote:
1. The second paragraph performs which of the following functions in the passage?

A. It describes a paradox that scientists were unable to resolve for some time.
B. It explains the effectiveness of a lethal biological pathogen.
C. It describes the mechanism by which a biological event occurs in humans.
D. It demonstrates how an infectious agent enters the human body.
E. It introduces information that is essential to understanding the role of Toxoplasma in human development.

Please explain.Why A is wrong ? and C correct, i choose A


Read Option A Carefully

A: It describes a paradox that scientists were unable to resolve for some time.

it says that Paragraph 2 describes the paradox, its not describing the Paradox , describing it would mean (detailing the paradox in detail , Something is happening and not sure why its happening)
Paradox is already stated in Paragraph 1, last few lines.

Paradox : A paradox is a statement that apparently contradicts itself and yet might be true.

Paragraph 2 sheds light on why its happening or Resolves the paradox, That's why A is wrong and C is correct.

A in fact is a Trap Answer Choice..
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Re: The single-celled parasite known as Toxoplasma gondii infects more  [#permalink]

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New post 04 Sep 2016, 00:11
2
Took 9 mins , including 3 mins to read :)

1(New) -
The second paragraph contains information describing the mechanism by which Toxoplasma is able to infiltrate the human body and remain undetected by the body's
immune system. We need to find an answer choice that reflects this.
(A) The paragraph does not summarize research that remains to be done. Instead, it discusses what has already been discovered.
(B) The paragraph does not present any recommendations.
(C) CORRECT. This matches our description of the paragraph.
(D) The paragraph does not introduce information about the role of Toxoplasma in human development. If anything, it introduces information about the role of humans
in the development of Toxoplasma.
(E) The paragraph does not mention any outdated scientific models.

2.The question asks us to infer something about Toxoplasma from the information given in the passage. When answering questions of this type, remember that GMAT
inferences are typically very close to the original text, although they never repeat information verbatim. Make sure to select an answer that is not stated explicitly but
can be inferred without making any additional assumptions.
(A) The passage does not suggest that the immune system will destroy Toxoplasma cells.
(B) The passage does not suggest that Toxoplasma collects in the lymphatic system.
(C) CORRECT. The passage states that Toxoplasma can reproduce only in a host cat. Therefore, any Toxoplasma cells that remain in the human body are not likely to reproduce.
(D) The passage does not suggest that Toxoplasma will be detected after several weeks.
(E) The passage does not suggest that Toxoplasma will be destroyed by pathogens in the bloodstream.

3.
We are asked to determine which one of the five choices is NOT true of Toxoplasma, according to the passage. In other words, four of the five choices are stated in the
passage and one choice is not. The choice that is not stated is the correct answer.
(A) The passage explicitly states that Toxoplasma can contaminate soil and water.
(B) The passage explicitly states that Toxoplasma enters the human body through contaminated food.
(C) The passage explicitly states that Toxoplasma alters the behavior of human dendritic cells.
(D) CORRECT. The word "incapable" in this answer choice is too strong; the passage does not state that the human body cannot detect Toxoplasma. Rather, it merely indicates that Toxoplasma does not trigger the body's immune system in the same way as other parasites. We have no information about the human body's ability to detect free-floating Toxoplasma cells.
(E) The passage explicitly states that Toxoplasma can breed in a host cat only.

4.
The question asks us to infer something about dendritic cells from the information contained in the passage. The correct answer must be based only on the information
contained in the passage. If any additional information is required to justify an answer choice, that choice cannot be the correct answer.
(A) The passage states only that dendritic cells are involved with the lymphatic system. No information is given as to the location of the cells' production.
(B) The passage states only that dendritic cells are common in the digestive tract. No information is given as to where the cells are most numerous.
(C) The passage states only that Toxoplasma infects dendritic cells. No information is given as to the proportion of the cells that are affected when a person is infected
with Toxoplasma.
(D) The passage states only that dendritic cells are capable of being infected with Toxoplasma. No information is given regarding any other types of cell.
(E) CORRECT. The passage states that Toxoplasma is capable of penetrating the barriers protecting the brain. The passage also states that Toxoplasma uses
dendritic cells as transport around the human body. Thus, we can infer that the Toxoplasma uses the dendritic cells to penetrate the barriers around the brain.

5.
The question asks us why the author mentions "pigs and chickens" in the final paragraph of the passage. The author mentions these animals in the context of
explaining how Toxoplasma enters the human body. Specifically, Toxoplasma enters the human body when humans ingest the meat of infected animals, "such as pigs
and chickens." So the author uses pigs and chickens as specific examples of animals that can carry the parasite.
(A) CORRECT. This matches our assessment of the passage exactly.
(B) The author mentions only "small rodents" as examples of animals that are eaten by cats.
(C) The author does not mention the dendritic cells of any animals other than humans.
(D) The passage states that cats are Toxoplasma's "sole breeding ground." Thus, the author could not mention the pigs and chickens as examples of animals in which
the parasite can breed.
(E) The author does not mention any animals at all that are immune to Toxoplasma.
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New post 04 Sep 2016, 23:29
1
e100 wrote:
Can someone explain third question?



3. Which of the following is the most likely outcome for Toxoplasma cells that invade the human body?

A. They will be destroyed by the immune system.
B. They will collect in the lymphatic system.
C. They will not reproduce.
D. They will be detected after several weeks.
E. They will be destroyed by other pathogens in the bloodstream.


The question asks us to infer something about Toxoplasma from the information given in the passage. When answering questions of this type, remember that GMAT
inferences are typically very close to the original text, although they never repeat information verbatim. Make sure to select an answer that is not stated explicitly but
can be inferred without making any additional assumptions.
(A) The passage does not suggest that the immune system will destroy Toxoplasma cells.
(B) The passage does not suggest that Toxoplasma collects in the lymphatic system.
(C) CORRECT. The passage states that Toxoplasma can reproduce only in a host cat. Therefore, any Toxoplasma cells that remain in the human body are not likely to reproduce.
(D) The passage does not suggest that Toxoplasma will be detected after several weeks.
(E) The passage does not suggest that Toxoplasma will be destroyed by pathogens in the bloodstream.
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New post 26 Jan 2018, 00:02
According to the passage, all of the following are true of Toxoplasma gondii EXCEPT
-it can contaminate ground water
-it enters the human body through the food chain
-it can alter the usual behavior of human cells
-the human body is incapable of detecting it
-it must find a host cat in order to reproduce

According to the 2nd para ,
Toxoplasma can alter the behaviour of the Dendritic Cells. Isn't option C too broad in scope to be right?
As for Option D , It isnt implied in the passage that it is not detected . Its only implied that no action is taken against the pathogen.

Please explain.
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New post 26 Jan 2018, 02:00
According to the passage, all of the following are true of Toxoplasma gondii EXCEPT
-it can contaminate ground water
-it enters the human body through the food chain
-it can alter the usual behavior of human cells
-the human body is incapable of detecting it
-it must find a host cat in order to reproduce

I was confused between A and D. First time, I chose A,
because there is a sentence 'These oocysts are shed in the cats' droppings and contaminate ground water~'
So I think water is contaminated not Toxoplasma but oocysts.
However, D is totally wrong, because scientests have found the fact that Toxoplasma is capable of hijacking dendritic cells.
It means that human body is capable of detecting Toxoplama gondii.
So OA is D.(Question 1 is hard to me..)



It can be inferred from the passage that which of the following statements is true of dendritic cells in the human body?
-They are produced by the lymphatic system.
-> incorrect. They are produced in the cat's intestines.
-They are more numerous in the digestive tract than in any other part of the human body.
-> Not mentioned
-Most dendritic cells of persons infected with Toxoplasma carry the parasite.
-> Wrong. Dendritic cells are hijacked by Toxoplasma, but it is hard to like C
Let's suppose there are x,yzC positions.
Hijacking is happened in z, we cannot say most dendritic cells are infected.
-They are the only cells capable of being infected by Toxoplasma.
-> Not mentioned about 'only cells'.
-They are able to penetrate the membranes surrounding the brain.
-> correct.



Which of the following is the most likely outcome for Toxoplasma cells that invade the human body?
-They will be destroyed by the immune system.
-> incorrect.
There is a clue in 1st sentence of 2nd paragraph
'scientists have discovered the parasite is quite common in certain cells,
known as dendritic ceels, involved in the human immune system,
: If A is correct, Toxoplasma cells cannot detected in certain cells, involved in the human immune system
-They will collect in the lymphatic system.
-> Not mentioned.
-They will not reproduce.
-> Correct
In last sentence, there are clues.
1. In fact, cats are a necessary component in the reproductive cycel of Toxoplasma,since the animal's intestines are the parasite's sole breeding ground.
2. Toxoplasma must somehow find its way into a new host cat in order to reproduce
: So C is correct
-They will be detected after several weeks.
-> Not mentioned
-They will be destroyed by other pathogens in the bloodstream.
-> Not mentioned



The second paragraph performs which of the following functions in the passage?

: 2nd paragraph explains about mechanism how Toxoplasma cells are not detected in human body.

A) It describes a paradox that scientists were unable to resolve for some time.
-> resolve? wrong.
B) It explains the effectiveness of a lethal biological pathogen.
-> effectiveness? wrong. 2nd paragraph just explains the mechanism.
C) It describes the mechanism by which a biological event occurs in humans.
-> correct
D) It demonstrates how the infectious agent reproduces itself.
-> 'reproduce' is mentioned in last paragraph, not 2nd paragraph
E) It introduces information that is essential to understanding the role of Toxoplasma in human development.
-> incorrect. There is no rold of Toxoplasma in human development.
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New post 09 Feb 2018, 00:05
Q1- According to the passage, all of the following are true of Toxoplasma gondii EXCEPT
-it can contaminate ground water - Clearly given
-it enters the human body through the food chain - Clearly given
-it can alter the usual behavior of human cells - It does so for the dendritic cells. Hold this one.
-the human body is incapable of detecting it - Hold this
-it must find a host cat in order to reproduce - Clearly given
Between C and D, since option C applies to a specific type of cell,that can pass. Also D is strengthened as the para 1 says that no immune response is generated by the body and it's still a puzzle.
hence ans- Option D

Q2-It can be inferred from the passage that which of the following statements is true of dendritic cells in the human body?
-They are produced by the lymphatic system. - Nowhere given
-They are more numerous in the digestive tract than in any other part of the human body. - are they even present in other part, unsure. Cancel this out.
-Most dendritic cells of persons infected with Toxoplasma carry the parasite. - Nowhere particularly mentioned
-They are the only cells capable of being infected by Toxoplasma. - Where has this been 'explicitly' mentioned?
-They are able to penetrate the membranes surrounding the brain. 'It can even penetrate the tight barrier that normally protects the brain from most pathogens. Yet, the blood of infected persons carries very few free-floating Toxoplasma cells. '

Q3- Which of the following is the most likely outcome for Toxoplasma cells that invade the human body?
-They will be destroyed by the immune system. - the immune system cannot understand them, so no!
-They will collect in the lymphatic system. - where is this said? No!
-They will not reproduce. - CORRECT. They can only reproduce inside a cat's body! '. In fact, cats are a necessary component in the reproductive cycle of Toxoplasma, since the animal's intestines are the parasite's sole breeding ground. '
-They will be detected after several weeks. - Cannot be infered
-They will be destroyed by other pathogens in the bloodstream.- NO. Nowhere mentioned

Q4- The second paragraph performs which of the following functions in the passage?
A) It describes a paradox that scientists were unable to resolve for some time. - Hold this
B) It explains the effectiveness of a lethal biological pathogen. - 'effectiveness?' - Nonsense
C) It describes the mechanism by which a biological event occurs in humans. -Hold this
D) It demonstrates how the infectious agent reproduces itself. - NO IT DOES NOT
E) It introduces information that is essential to understanding the role of Toxoplasma in human development. - Lol. toxoplasma and Human Development- Poles apart
Now between A and C.
Now although A seems tempting, there is no 'paradox' Paradox means contradiction. There's no contradiction here. It is just another topic that was unclear but latest research has shed some light on it. No opposing views. Hence, it is wrong. Correct answer hence is C.

Hope this helps. Hit Kudos if it does or if you like it :)
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New post 16 May 2018, 01:58
This looks very much unlike the GMAT Standard RC , So much Confusion

Question 1

Why not choice C - It talks of human cell , specifically its dendritic cell , so we can narrow down to C ,

but wait :p :dream:

Choice E is a strong contender because (even rodent can be a host for Toxoplasma)

para 3 :-
" Toxoplasma must somehow find its way into a new host cat in order to reproduce, it cannot kill its current host. Instead, it waits for the host, usually a small rodent, to be eaten by a cat, thus providing Toxoplasma the opportunity to reproduce"


Question 4 can not be A , even i answered A , i think it is wrong , because its not describing the Paradox , which is " the ability of Toxoplasma to parasitize the human body without triggering an immune response and without an appreciable presence in the bloodstream " , it is resolving the paradox by telling the biological mechanism.
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