RC question - Toxoplasma - Except

[umamakesh.n]

Passage


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.

Toxoplasma - Except

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

A it can contaminate ground water[/list]

B it enters the human body through the food chain[/list]

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

I am having trouble understanding the generalization in choice III
The passage says it can alter the usual behaviour of human dendritic cells, whereas Choice III is: it can alter the usual behavior of human cells. IMO, toxoplasma could affect dendritic cells only and may be few other cells, but choice III seems broad as it encompasses all human cells. I dont know how to eliminate it on this basis.

P.S the answer is IV.

Your help is much appreciated.!

-Uma

[RonPurewal]

hi -

i understand what you're saying here, but you're misinterpreting the language of the answer choice.

in general, if you say "X can VERB OBJECTs", or "X has VERBed OBJECTs", or other such statements, then the default interpretation is that this is a true statement if this can happen for any OBJECTs.

in other words, the statement is the same as it would be with the insertion of "some".

here are some examples:
i've eaten pakistani food.
--> this is a true statement if i've ever eaten pakistani food. i don't have to have tried everything on the menu.

i can draw human hands.
--> still a true statement even if i can't draw, say, babies' or elderly people's hands.

etc.

--

you do, however, have a good point. we should probably add the word "some" to the answer choice, just to make it clearer.

i will submit this problem for revision.

[natzmyid]

Hi Ron,

(edited) My doubt is with the above question. Choice 3 seems to be the right answer.

It is not mentioned anywhere in the passage that Toxoplasma gondii alters the behavior of human/dentritic cells. However, it is mentioned that Toxoplasma uses dendrititic cells for transportation. But it doesn't seem to imply that the cell's behavior is changed as a result.

Please guide me as to what I am missing here. Thanks!

[RonPurewal]

Hi Ron,

(edited) My doubt is with the above question. Choice 3 seems to be the right answer.

It is not mentioned anywhere in the passage that Toxoplasma gondii alters the behavior of human/dentritic cells. However, it is mentioned that Toxoplasma uses dendrititic cells for transportation. But it doesn't seem to imply that the cell's behavior is changed as a result.

Please guide me as to what I am missing here. Thanks!

but it does say that the bacterium changes the usual behavior of the cells. see here:
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.

the boldfaced words prove that the bacterium is actually changing the cell's normal behavior.

[chetan.dodiya86]

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.

I have questions regarding answer options C and A.

In the first paragraph, last 2 lines are mentioned as :
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.

So the next paragraph would most probably explain the research and outcome of it.

By doing POE, I left with option A.
Option C says -It describes the mechanism by which a biological event occurs in humans.

Q. -> Scope of option C is not too broad? Does second paragraph covers biological event occurs in complete human body? And also, does it covers all the biological events occur in human?

Could you please explain why A is wrong and C is right?
Am I misreading something?

[Danna]

"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. "


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

E it must find a host cat in order to reproduce

Hi instructors,
I know E misrepresents the information in the passage, but I don't understand how it works...
What is the difference between E and the boldface in the passage?

[harika.apu]

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.

I have questions regarding answer options C and A.

In the first paragraph, last 2 lines are mentioned as :
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.

So the next paragraph would most probably explain the research and outcome of it.

By doing POE, I left with option A.
Option C says -It describes the mechanism by which a biological event occurs in humans.

Q. -> Scope of option C is not too broad? Does second paragraph covers biological event occurs in complete human body? And also, does it covers all the biological events occur in human?

Could you please explain why A is wrong and C is right?
Am I misreading something?

Hello, Even i have same doubt
according to c ->it gives info about how information about pathogens is carried to lymph nodes
But second paragraph also explain how Toxoplasma hi-jack them
Moreover, i think second paragraph info about (dendrite cells carrying info regrading pathogens) is stated to show how toxoplasma divert them from doing the former activity
Can anyone tell my reasoning is right ?

[ankur.mittal09]

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.

Hi Experts,

I am wondering why B is incorrect. I know that C is correct as stated in 3rd para that -cats are a necessary component in the reproductive cycle of Toxoplasma.
Just wanted to clear my understanding of why option B is incorrect:-
2nd para says that Toxoplasma hijacks dendritic cells that travel to lymph nodes.
but then it says that toxoplasma force them to divert from their usual activity(i.e. informing the lymph nodes probably) and use them as transport system.
Can you please let me know if the above reasoning is correct ?
Thanks.