The survival of nerve cells, as well as their performance of some spec

Question

The survival of nerve cells, as well as their
performance of some specialized functions, is
regulated by chemicals known as neurotrophic
factors, which are produced in the bodies of animals,
  (5)   including humans. Rita Levi-Montalcini’s discovery
in the 1950s of the first of these agents, a
hormonelike substance now known as NGF, was a
crucial development in the history of biochemistry,
which led to Levi-Montalcini sharing the Nobel Prize
  (10)   for medicine in 1986.

In the mid-1940s, Levi-Montalcini had begun by
hypothesizing that many of the immature nerve cells
produced in the development of an organism are
normally programmed to die. In order to confirm this
  (15)   theory, she conducted research that in 1949 found
that, when embryos are in the process of forming
their nervous systems, they produce many more nerve
cells than are finally required, the number that
survives eventually adjusting itself to the volume of
  (20)   tissue to be supplied with nerves. A further phase of
the experimentation, which led to Levi-Montalcini’s
identification of the substance that controls this
process, began with her observation that the
development of nerves in chick embryos could be
  (25)   stimulated by implanting a certain variety of mouse
tumor in the embryos. She theorized that a chemical
produced by the tumors was responsible for the
observed nerve growth. To investigate this hypothesis,
she used the then new technique of tissue culture, by
  (30)   which specific types of body cells can be made to
grow outside the organism from which they are
derived. Within twenty-four hours, her tissue cultures
of chick embryo extracts developed dense halos of
nerve tissue near the places in the culture where she
  (35)   had added the mouse tumor. Further research
identified a specific substance contributed by the
mouse tumors that was responsible for the effects
Levi-Montalcini had observed: a protein that she
named “nerve growth factor” (NGF).

(40)   NGF was the first of many cell-growth factors to
be found in the bodies of animals. Through Levi
Montalcini’s work and other subsequent research, it
has been determined that this substance is present in
many tissues and biological fluids, and that it is
  (45)   especially concentrated in some organs. In developing
organisms, nerve cells apparently receive this growth
factor locally from the cells of muscles or other
organs to which they will form connections for
transmission of nerve impulses, and sometimes from
  (50)   supporting cells intermingled with the nerve tissue.
NGF seems to play two roles, serving initially to
direct the developing nerve processes toward the
correct, specific “target” cells with which they must
connect, and later being necessary for the continued
  (55)   survival of those nerve cells. During some periods of
their development, the types of nerve cells that are
affected by NGF—primarily cells outside the brain
and spinal cord—die if the factor is not present or if
they encounter anti-NGF antibodies.    1 
 1. Which one of the following most accurately expresses the main point of the passage?

(A) Levi-Montalcini’s discovery of neurotrophic factors as a result of research carried out in the 1940s was a major contribution to our understanding of the role of naturally occurring chemicals, especially NGF, in the development of chick embryos.
(B) Levi-Montalcini’s discovery of NGF, a neurotrophic factor that stimulates the development of some types of nerve tissue and whose presence or absence in surrounding cells helps determine whether particular nerve cells will survive, was a pivotal development in biochemistry.
(C) NGF, which is necessary for the survival and proper functioning of nerve cells, was discovered by Levi-Montalcini in a series of experiments using the technique of tissue culture, which she devised in the 1940s.
(D) Partly as a result of Levi-Montalcini’s research, it has been found that NGF and other neurotrophic factors are produced only by tissues to which nerves are already connected and that the presence of these factors is necessary for the health and proper functioning of nervous systems.
(E) NGF, a chemical that was discovered by LeviMontalcini, directs the growth of nerve cells toward the cells with which they must connect and ensures the survival of those nerve cells throughout the life of the organism except when the organism produces anti-NGF antibodies.

2 
 2. Based on the passage, the author would be most likely to believe that Levi-Montalcini’s discovery of NGF is noteworthy primarily because it

(A) paved the way for more specific knowledge of the processes governing the development of the nervous system
(B) demonstrated that a then new laboratory technique could yield important and unanticipated experimental results
(C) confirmed the hypothesis that many of a developing organism’s immature nerve cells are normally programmed to die
(D) indicated that this substance stimulates observable biochemical reactions in the tissues of different species
(E) identified a specific substance, produced by mouse tumors, that can be used to stimulate nerve cell growth

3 
 3. The primary function of the third paragraph of the passage in relation to the second paragraph is to

(A) indicate that conclusions referred to in the second paragraph, though essentially correct, require further verification
(B) indicate that conclusions referred to in the second paragraph have been undermined by subsequently obtained evidence
(C) indicate ways in which conclusions referred to in the second paragraph have been further corroborated and refined
(D) describe subsequent discoveries of substances analogous to the substance discussed in the second paragraph
(E) indicate that experimental procedures discussed in the second paragraph have been supplanted by more precise techniques described in the third paragraph

4 
 4. Information in the passage most strongly supports which one of the following?

(A) Nerve cells in excess of those that are needed by the organism in which they develop eventually produce anti-NGF antibodies to suppress the effects of NGF.
(B) Nerve cells that grow in the absence of NGF are less numerous than, but qualitatively identical to, those that grow in the presence of NGF.
(C) Few of the nerve cells that connect with target cells toward which NGF directs them are needed by the organism in which they develop.
(D) Some of the nerve cells that grow in the presence of NGF are eventually converted to other types of living tissue by neurotrophic factors.
(E) Some of the nerve cells that grow in an embryo do not connect with any particular target cells.

5 
 5. The passage describes a specific experiment that tested which one of the following hypotheses?

(A) A certain kind of mouse tumor produces a chemical that stimulates the growth of nerve cells.
(B) Developing embryos initially grow many more nerve cells than they will eventually require.
(C) In addition to NGF, there are several other important neurotrophic factors regulating cell survival and function.
(D) Certain organs contain NGF in concentrations much higher than in the surrounding tissue.
(E) Certain nerve cells are supplied with NGF by the muscle cells to which they are connected.

6 
 6. Which one of the following is most strongly supported by the information in the passage?

(A) Some of the effects that the author describes as occurring in Levi-Montalcini’s culture of chick embryo extract were due to neurotrophic factors other than NGF.
(B) Although NGF was the first neurotrophic factor to be identified, some other such factors are now more thoroughly understood.
(C) In her research in the 1940s and 1950s, LeviMontalcini identified other neurotrophic factors in addition to NGF.
(D) Some neurotrophic factors other than NGF perform functions that are not specifically identified in the passage.
(E) The effects of NGF that Levi-Montalcini noted in her chick embryo experiment are also caused by other neurotrophic factors not discussed in the passage.

Source:   LSAT Official PrepTest 44   
 Difficulty Level:   700+

RC Butler 2021  -  Practice Two RC Questions Everyday.   
Passage # 306 Date: 05-Aug-2021
 This question is a part of RC Butler 2021 .  Click here for Details

Mom789 · Answer

please explain question answere with explanation

Sajjad1994 · Answer

Please mention the question number(s) you want to get explained.

Thank you!

FauleKatze · Answer

Hi, can someone please explain questions 1, 2, 5, and 6? 
Thanks in advance!

iridescent995 · Answer

Can any one explain why Q6 answer is not E (The effects of NGF that Levi-Montalcini noted in her chick embryo experiment are also caused by other neurotrophic factors not discussed in the passage.), it is directly implied by the first line of para 3 " NGF was the first of many cell-growth factors to be found in the bodies of animals. "?

MBAB123 · Answer

iridescent995 , it's actually not directly implied from the line you quoted. How do you know what those other Neurotrophic factors do? Levi-Montalcini doesn't even mention them in her experiment. I agree that it is entirely possible for the other neurotrophic factors also cause the effects noted by Levi, but we don't know that for sure. Option D is much safer bet.

carouselambra · Answer

Can we have the OEs for Q4 and Q5?
Have to say, insane questions!!

Cheers.

Sajjad1994 · Answer

Explanation

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

Difficulty Level:   650

Explanation

The point is that, in a lengthy wrong choice, some of its prose will reflect the passage accurately, so you need to bore through the verbiage to find the categorical ways in which four of the choices go astray. Otherwise, you’ll get bogged down in things that sound good even if you’ve already armed yourself with a prediction. Take  (A) , for instance. Levi-Montalcini did make a discovery, and it was a big deal, and it did involve research begun in the 1940s. All of that is right. But the passage doesn’t say that Levi-Montalcini discovered  “neurotrophic factors,”  only that she discovered the first of them, NGF. Moreover, as  (A)  is worded, her work is most noteworthy for what it taught us about chick embryos. Say what? Levi-Montalcini used chick embryos in her research, but her Nobelwinning findings clearly have impact on many animals beyond baby chicks—most notably, humans. Get the idea? By zeroing in on one or more categorical ways in which a lengthy choice goes wrong, you can quickly eliminate tricky but ultimately incorrect answers.

(B)  The main clause is,  “The discovery...was pivotal.”  Quite right; that reflects the one subjective statement in the entire passage, made in  lines 5–10.  Does the rest of  (B)  accurately reflect the passage? Yes, the appositive (the modifying phrase between commas) deftly sums up the  “two roles”  discussed in  lines 51–59.  And is there a sin of omission? No, everything important is summed up here. But perhaps you’ll want to confirm that the remaining choices are bad before making your final selection.

(C)  emphasizes NGF’s role in keeping nerve cells alive (overlooking those cells’ development), makes  “tissue culture”  (which was only introduced in line 29) central to Levi-Montalcini’s work, and ascribes the devising of tissue culture to her. All of that is bogus.

(D)  How NGF is produced is never described in the passage (it’s all about how Levi-Montalcini found it, and what it does). Moreover, to say that NGF  “is necessary for the health and proper functioning of nervous systems”  goes much further than  lines 54–55.  And since the star of the passage is LeviMontalcini, it seems odd to diminish her work as only  “partly”  responsible.

(E)  gives short shrift to Levi-Montalcini’s discovery process and its importance and hence to the first twothirds of the passage. Meanwhile, its main clause focuses only on  lines 51–59 , and distorts them to boot (the final  “except”  clause is tossed in and turns the choice into gibberish). We’re left with our initial impression that (B) is the one and only nonflawed answer.

Answer: B

2. Based on the passage, the author would be most likely to believe that Levi-Montalcini’s discovery of NGF is noteworthy primarily because it

Difficulty Level:   650

Explanation

The noteworthiness of the NGF discovery is mentioned in  paragraph 1 , but comes back again in  paragraph 3 , and we ought to review both. Neurotrophic factors like NGF certainly sound important as far as  paragraph 1  goes, and their importance is reinforced later by references to: NGF’s being  “the first of many” (line 40); “subsequent research” (line 42)  that has found NGF throughout the body; and the chemical’s two roles  (lines 51–59) . All of that is summed up in  (A) . As the first discovered neurotrophic factor, NGF did  “pave the way,”  and there’s little doubt as to the  “specificity”  of the knowledge sketched out in  paragraph 3.

(B)  There’s no sense that finding NGF was  “unanticipated.”  Indeed, much of Levi-Montalcini’s work seems to have confirmed hypotheses she already held.

(C)  The normal programming of immature cells to die should have struck you as a rather marginal affair, hardly meriting the term  “noteworthy,”  especially since the issue never comes up in  paragraph 3. (C)  just echoes Levi-Montalcini’s initial hypothesis  (lines 11–14) , which was not the endpoint of her research but the beginning: figuring that the cells were programmed to die, she asked the question  “Why?,”  a quest that led her ultimately to NGF.

(D)  This choice does not match up at all with the two roles played by NGF, at least on the strength of  lines 51–59.  This vague statement is unsupported by the passage.

(E)  This choice blows up the importance of mouse tumors (NGF, remember, is found in many animals), and  “can be used to stimulate”  wrongly implies that NGF is some sort of applied substance, rather than one occurring naturally in animals’ bodies.

Answer: A

5. The passage describes a specific experiment that tested which one of the following hypotheses?

Difficulty Level:   700

Explanation

A couple of Levi-Montalcini’s hypotheses are mentioned here and there. But if you circled the phrase  “To investigate that hypothesis” (line 28)  and saw that an experiment is described immediately afterward, you probably had little difficulty settling on  (A) , which describes the hypothesis in  lines 26–28  that the subsequent experiment  (lines 29–35)  was designed to test.

(B)  mentions a finding of Levi-Montalcini’s  (lines 15–18) , not a hypothesis for which an experiment was designed.

(C) Lines 1–5  and  lines 40–41  hint at other neurotrophic factors, but the passage falls far short of describing them, let alone presenting an experiment designed to confirm their existence.

(D)  No reference to differing levels of NGF is made anywhere in the passage.

(E) , like  (B) , offers a research finding (this one, a discovery not necessarily made by Levi-Montalcini, is mentioned in  lines 45–49 ), but no experiment backing it up is described.

Answer: A

6. Which one of the following is most strongly supported by the information in the passage?

Difficulty Level:   750

Explanation

All five choices allude to the neurotrophic factors other than NGF—neurotrophic factors that are mentioned briefly early on, and again later, but that play no important role in the overall text. Let’s take them in order:

(A)  Neurotrophic factors other than NGF never come up in the discussion of Levi-Montalcini’s work with chick embryos.

(B)  A statement that’s far from inferable. Yes, neurotrophic factors other than NGF are known, but who’s to say that they’re better comprehended? Besides, if longevity is relevant here, then logic suggests that NGF—discovered first—would be known best of all.

(C)  There’s no justification for attributing the other neurotrophic factors’ discovery to Levi-Montalcini. As far as we know from the passage, Levi-Montalcini worked on NGF and nothing else.

(D)  Here’s the one and only verifiable fact about other neurotrophic factors.  Lines 1–6  confirm that there are more of them than just NGF, and the first two lines strongly suggest that they have other “specialized functions” that the passage never describes.  (D)  is correct.

(E)  is almost functionally identical to  (A) , and is every bit as wrong. As far as we know, Levi-Montalcini’s chick embryo work involved NGF and nothing else.

Answer: D

Sajjad1994 · Answer

Explanation

4. Information in the passage most strongly supports which one of the following?

Difficulty Level:   750

Explanation

This one is tough: No assistance is offered in the stem, and the choices offer a lot of detail that’s going to require you to work slowly and painfully through  paragraph 2 . Most students would do well to write this one off, especially given how much easier the next question is. For those who did try this, there’s no alternative but to assess each of the choices.

(A)  combines  lines 15–20  and  line 59  into one big fat distortion. The self-adjustment process mentioned in the former has no connection to the antibodies mentioned in the latter.

(B)  makes an unwarranted comparison between two types of nerve cells, and the phrase  “qualitatively identical”  offers a level of precision not justified by
anything in the text.

(C)  Opposite: the sense offered in  paragraph 3  is that NGF directs necessary cells to the place where they’re needed.

(D)  hints at a  “conversion”  or transformation that has no basis in the text. Besides,  (D)  implies that NGF and neurotrophic factor are different things, whereas the first is actually an example of the second.

(E)  The only one left must be inferable, and it is. According to  lines 45–50 , nerve cells can receive NGF

Answer: E

For question number 5  click here

TargetKellogg2024 · Answer

Such a great passage! We need more of the kind to practice for our RC

AliGmz · Answer

Sajjad1994 , I would like to point out a nuance regarding the explanation to the answer choice D of question 6. "The functions" mentioned in the line 2, are the functions performed by NERVE CELLS, NOT by NEUROTROPHIC FATORS. As per the passage, NFs regulate 1) performance of nerve cells and 2) survival of them. How can we infer that NFs other than NGFs perform OTHER functions not mentioned in the passage?

Another thing: the effects mentioned in Ac D are about NERVE CELL GROWTH. Line 40: "NGF was the first of many cell-growth factors to
be found in the bodies of animals". Inference:  The effects (NERVE CELL GROWTH)  of NGF that Levi-Montalcini noted in her chick embryo experiment  are also caused by other neurotrophic factors not discussed in the passage . How come is this inference incorrect?

AliGmz · Answer

@  GMATNinja , please give us a hand.

The survival of nerve cells, as well as their performance of some spec

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The survival of nerve cells, as well as their performance of some spec

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