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Manhattan RC: Toxoplasma gondii (The trickiest RC so far)

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joealam1 Senior | Next Rank: 100 Posts Default Avatar
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Manhattan RC: Toxoplasma gondii (The trickiest RC so far)

Post Tue Nov 29, 2016 10:55 pm
Elapsed Time: 00:00
  • Lap #[LAPCOUNT] ([LAPTIME])
    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) 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.

    OA:E
    I didn't get why B is wrong, it is mentioned clearly in the passage that"Dendritic cells are found in the digestive tract" which means that they are not found elsewhere

    2)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

    OA: D

    3)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.

    OA: C

    on the 1st paragprah the author mentioned at the end that new research has helped in unraveling the paradox, paragraph 2 is explaining this paradox so why A is wrong?

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    Marty Murray Legendary Member
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    Post Fri Dec 02, 2016 10:01 pm
    joealam1 wrote:
    1) 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.

    OA:E
    I didn't get why B is wrong, it is mentioned clearly in the passage that"Dendritic cells are found in the digestive tract" which means that they are not found elsewhere
    What you did is a classic way to get an inference question wrong.

    If I say "There is a dog in the yard," does that mean that there it not a dog in the dining room? Only if you start making things up that are not said, and making things up that are not either said or logically supported is one way in which people get inference questions wrong.

    "Dendritic cells are found in the digestive tract" means just one thing, that they are found there. It does not mean that they are not found anywhere else. It may sound a bit as if it means that they are not found anywhere else, but really it does not state that they are not found anywhere else.

    Moreover, getting Reading Comprehension questions right takes noticing key details. In this case, a little further along are details "When the dendritic cells encounter pathogens, they travel to lymph nodes," and "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." Those statements indicate that dentritic cells can be and are found in places other than in the digestive tract.

    Quote:
    3)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.

    OA: C

    on the 1st paragprah the author mentioned at the end that new research has helped in unraveling the paradox, paragraph 2 is explaining this paradox so why A is wrong?
    You said it yourself. Paragraph 2 does not describe the paradox. It explains what underlies the seeming paradox.

    Once again, noticing a key detail, in this case the word "describes" in the answer choice, is key for getting the question right.

    Likely you won't get RC questions right consistently by choosing answers that seem vaguely correct. You have to be super careful about details and really make sure that the answers you choose are EXACTLY correct.

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