All of the cells in a particular plant start out with the same

Question

All of the cells in a particular plant start out with the same complement of genes. How then can these cells differentiate and form structures as different as roots, stems, leaves, and fruits? The answer is that only a small subset of the genes in a particular kind of cell are expressed, or turned on, at a given time. This is accomplished by a complex system of chemical messengers that in plants include hormones and other regulatory molecules. Five major hormones have been identified: auxin, abscisic acid, cytokinin, ethylene, and gibberellin. Studies of plants have now identified a new class of regulatory molecules called oligosaccharins.

Unlike the oligosaccharins, the five well-known plant hormones are pleiotropic rather than specific; that is, each has more than one effect on the growth and development of plants. The five has so many simultaneous effects that they are not very useful in artificially controlling the growth of crops. Auxin, for instance, stimulates the rate of cell elongation, causes shoots to grow up and roots to grow down, and inhibits the growth of lateral shoots. Auxin also causes the plant to develop a vascular system, to form lateral roots, and to produce ethylene.

The pleiotropy of the five well-studied plant hormones is somewhat analogous to that of certain hormones in animal. For example, hormones from the hypothalamus in the brain stimulate the anterior lobe of the pituitary gland to synthesize and release many different hormones, one of which stimulates the release of hormones from the adrenal cortex. These hormones have specific effects on target organs all over the body. One hormone stimulates the thyroid gland, for example, another the ovarian follicle cells, and so forth. In other words, there is a hierarchy of hormones.

Such a hierarchy may also exist in plants. Oligosaccharins are fragments of the cell wall released by enzymes: different enzymes release different oligosaccharins. There are indications that pleiotropic plant hormones may actually function by activating the enzymes that release these other, more specific chemical messengers from the cell wall.

1. According to the passage, the five well-known plant hormones are not useful in controlling the growth of crops because

(A) it is not known exactly what functions the hormones perform
(B) each hormone has various effects on plants
(C) none of the hormones can function without the others
(D) each hormone has different effects on different kinds of plants
(E) each hormone works on only a small subset of a cell's genes at any particular time

Show Spoiler

Supporting ideas

To answer this question, look for information that is provided in the passage. Lines 16–20 explain that each of the five plant hormones has more than one effect on the growth and development of plants; for this reason, they are not very useful in artificially controlling the growth of crops.

A Lines 20–25 describe in detail the multiple functions of the hormone auxin.

B Correct. The hormones have so many simultaneous effects on plants that they are not useful in controlling the growth of crops.

C The passage provides no evidence to support this reason.

D No information is given in the passage to support this reason.

E The hormones’ multiple effects on plant growth, not their specific effect at the cellular level, make them ineffective at artificially controlling crop growth.

The correct answer is B.

2. The passage suggests that the place of hypothalamic hormones in the hormonal hierarchies of animals is similar to the place of which of the following in plants?

(A) plant cell walls
(B) the complement of genes in each plant cell
(C) a subset of a plant cell's gene complement
(D) the five major hormones
(E) the oligosaccharins

3. The passage suggests that which of the following is a function likely to be performed by an oligosaccharin?

(A) to stimulate a particular plant cell to become part of a plant's root system
(B) to stimulate the walls of a particular cell to produce other oligosaccharins
(C) to activate enzymes that release specific chemical messengers from plant cell walls
(D) to duplicate the gene complement in a particular plant cell
(E) to produce multiple effects on a particular subsystem of plant cells

4. The author mentions specific effects that auxin has on plant development in order to illustrate the

(A) point that some of the effects of plant hormones can be harmful
(B) way in which hormones are produced by plants
(C) hierarchical nature of the functioning of plant hormones
(D) differences among the best-known plant hormones
(E) concept of pleiotropy as it is exhibited by plant hormones

5. According to the passage, which of the following best describes a function performed by oligosaccharins?

(A) regulating the daily functioning of a plant's cells
(B) interacting with one another to produce different chemicals
(C) releasing specific chemical messengers from a plant's cell walls
(D) producing the hormones that cause plant cells to differentiate to perform different functions
(E) influencing the development of a plant's cells by controlling the expression of the cells' genes

6. The passage suggests that, unlike the pleiotropic hormones, oligosaccharins could be used effectively to

(A) trace the passage of chemicals through the walls of cells
(B) pinpoint functions of other plant hormones
(C) artificially control specific aspects of the development of crops
(D) alter the complement of genes in the cells of plants
(E) alter the effects of the five major hormones on plant development

7. The author discusses animal hormones primarily in order to

(A) introduce the idea of a hierarchy of hormones
(B) explain the effects that auxin has on plant cells
(C) contrast the functioning of plant hormones and animals hormones
(D) illustrate the way in which particular hormones affect animals
(E) explain the distinction between hormones and regulatory molecules

Show Spoiler

JOURNAL ARTICLE
Oligosaccharins
Peter Albersheim and Alan G. Darvill
Scientific American
Vol. 253, No. 3 (September 1985), pp. 58-65
Published by: Scientific American, a division of Nature America, Inc.
https://www.jstor.org/stable/24967788
Page Count: 8

Attachment:

Oligosaccharins.pdf

GMATNinja · Accepted Answer

The passage tells us that "a complex system of chemical messengers that in plants include hormones and other regulatory molecules" allows cells to "differentiate and form structures as different as roots, stems, leaves, and fruits." Furthermore, the passage tells us that the five well-known hormones, which are "pleiotropic" ("P's") because they have multiple effects, might function by activating certain enzymes that in turn release regulatory molecules called oligosaccharins ("O's"), which, because they are not "P's", have only one specific effect on the growth and development of plants.

In other words, the five "P's" activate enzymes which in turn release "O's", which have a single, specific effect on the growth and development of the plant (for example, forming roots, stems, leaves, or fruits). Thus, the passage suggests that the "O's" could be directly responsible for causing a plant cell to become part of a plant's root system. Thus, choice (A) is the best answer.

As explained above, the "O's" have one specific effect on the growth and development of plants. How is this possible, when "all of the cells in a particular plant start out with the same complement of genes"? It's because "only a small subset of the genes in a particular kind of cell are expressed, or turned on, at a given time." Thus, it makes sense that the "O's" could function by "influencing the development of a plant's cells by controlling the expression of the cells' genes", as described in choice (E).

(D) cannot be the answer because we are not told that the "O's" produce hormones. Rather, as described above, the "P" hormones activate enzymes that release "O" regulatory molecules, which in turn cause plant cells to differentiate and perform different functions.

I hope that helps!

JarvisR · Answer

10 mins.
1. according to the passage, the five well-known plant hormones are not useful in controlling the growth of crops because
(a) it is not known exactly what functions the hormones perform
(b) each hormone has various effects on plants
>> unlike the oligosaccharins, the five well-known plant hormones are pleiotropic rather than specific,
(c) none of the hormones can function without the others
(d) each hormone has different effects on different kinds of plants
(e) each hormone works on only a small subset of a cell's genes at any particular time

2. the passage suggests that the place of hypothalamic hormones in the hormonal hierarchies of animals is similar to the place of which of the following in plants?
(a) plant cell walls
(b) the complement of genes in each plant cell
(c) a subset of a plant cell's gene complement
(d) the five major hormones
>> Animal hormones example is presented to present the idea of hormone hierarchy in plants.
(e) the oligosaccharins

3. the passage suggests that which of the following is a function likely to be performed by an oligosaccharin?
(a) to stimulate a particular plant cell to become part of a plant's root system
>> unlike the oligosaccharins, the five well-known plant hormones are pleiotropic rather than specific,
(b) to stimulate the walls of a particular cell to produce other oligosaccharins
(c) to activate enzymes that release specific chemical messengers from plant cell walls
(d) to duplicate the gene complement in a particular plant cell
(e) to produce multiple effects on a particular subsystem of plant cells

4. the author mentions specific effects that auxin has on plant development in order to illustrate the
(a) point that some of the effects of plant hormones can be harmful
(b) way in which hormones are produced by plants
(c) hierarchical nature of the functioning of plant hormones
(d) differences among the best-known plant hormones
(e) concept of pleiotropy as it is exhibited by plant hormones
>>the five well-known plant hormones are pleiotropic rather than specific.Since auxin has multiple effects.

5. according to the passage, which of the following best describes a function performed by oligosaccharins?
(a) regulating the daily functioning of a plant's cells
(b) interacting with one another to produce different chemicals
(c) releasing specific chemical messengers from a plant's cell walls
(d) producing the hormones that cause plant cells to differentiate to perform different functions
(e) influencing the development of a plant's cells by controlling the expression of the cells' genes
>> unlike the oligosaccharins, the five well-known plant hormones are pleiotropic rather than specific,

6. the passage suggests that, unlike the pleiotropic hormones, oligosaccharins could be used effectively to
(a) trace the passage of chemicals through the walls of cells
(b) pinpoint functions of other plant hormones
(c) artificially control specific aspects of the development of crops
>> Unlike P, O can influence specific property.
(d) alter the complement of genes in the cells of plants
(e) alter the effects of the five major hormones on plant development

7. the author discusses animal hormones primarily in order to
(a) introduce the idea of a hierarchy of hormones
>>the pleiotropy of the five well-studied plant <b>(25)</b> hormones is somewhat analogous to that of certain hormones in animal.
(b) explain the effects that auxin has on plant cells
(c) contrast the functioning of plant hormones and animals hormones
(d) illustrate the way in which particular hormones affect animals
(e) explain the distinction between hormones and regulatory molecules

Study1 · Answer

5. According to the passage, which of the following best describes a function performed by oligosaccharins?

The genes in a particular kind of cell...are expressed, or turned on,...by a complex system of chemical messengers that include...regulatory molecules...called oligosaccharins. (Paragraph 1)

Reverse the reverb to get D ("Influencing the development of a plant’s cells by controlling the expression of the cells’ genes").

Oligosaccharins are regulatory molecules that are chemical messengers and that turn on or express the genes in a particular kind of cell.

jerrykid · Answer

I finally found out the answer. This question is very complicated. It took me half an hour to crack this question.

D is the correct answer.

According to the passage:

"The pleiotropy of the five well-studied plant hormones is somewhat analogous to that of certain hormones in animal. For example, hormones from the hypothalamus in the brain stimulate the anterior lobe of the pituitary gland to synthesize and release many different hormones, one of which stimulates the release of hormones from the adrenal cortex. These hormones have specific effects on target organs all over the body. One hormone stimulates the thyroid gland, for example, another the ovarian follicle cells, and so forth. In other words, there is a hierarchy of hormones. Such a hierarchy may also exist in plants. Oligosaccharins are fragments of the cell wall released by enzymes: different enzymes release different oligosaccharins. There are indications that pleiotropic plant hormones may actually function by activating the enzymes that release these other, more specific chemical messengers from the cell wall.

The processes in animals and in plants could be summarized as followed:

In animals: hypothalamus --> synthesize and release many different hormones --> one hormones stimulates the release of hormones from the adrenal cortex --> effects on target organs

In plants: pleiotropic plant hormones --> enzymes --> Oligosaccharins i.e. fragments of the cell wall released by enzymes --> different enzymes release different oligosaccharins

So hypothalamus can be inferred to function as pleiotropic plant hormones do.

anikacr7 · Answer

Answer to question 3 and 5 please, with explanation.
Plus, for question 5, the last line says that there are indications hormones might work by activating enzymes that release oligosaccharins, so why is d not the answer for 5

kkrrsshh · Answer

For Q3, agreed that Oligosachhariins perform specific function and plant root system is specific. But arent we inferring too far here because there is nothing mentioned in passage about oligosachharin and root system. Passage just mentions specific function:It can be any specific function but we dont know that from passage.
Please, can anyone throw light on this.

abhimahna · Answer

Hi  kkrrsshh  ,

I agree with your point. But notice the wording of the question. It says "likely" to be performed.

This means we need to find out an option that says the function is specific rather than generic. Hence, only option A does so. Thus, the correct answer.

oasis90 · Answer

Hi  jennpt

5. According to the passage, which of the following best describes a function performed by oligosaccharins?

(A) regulating the daily functioning of a plant's cells

(B) interacting with one another to produce different chemicals

(C) releasing specific chemical messengers from a plant's cell walls

(D) producing the hormones that cause plant cells to differentiate to perform different functions

(E) influencing the development of a plant's cells by controlling the expression of the cells' genes

This feels to me like an inference questions. E is no where stated explicitly. I struggled with this because I couldn't find definitive evidence for E.

Thanks a ton.

BrightOutlookJenn · Answer

Hi  oasis90

Your evidence is the first paragraph (bolding mine):

To simplify these sentences, differentiation happens because of gene expression. Gene expression is "accomplished by" (I might say just "done by") chemical messengers including "other regulatory molecules." Oligosaccharins are one of these "other regulatory molecules." So, oligosaccharins accomplish gene expression that tells cells to differentiate.

So here we have to basically summarize/collapse five sentences into one - but the evidence is there. 
Does this help?

oasis90 · Answer

jennpt

Wow! That requires some serious active reading. I need to watch out for those. Thanks a lot. I take it this is the reason A is the answer for question 3 below ?

3. The passage suggests that which of the following is a function likely to be performed by an oligosaccharin?

(A) to stimulate a particular plant cell to become part of a plant's root system

(B) to stimulate the walls of a particular cell to produce other oligosaccharins

(C) to activate enzymes that release specific chemical messengers from plant cell walls

(D) to duplicate the gene complement in a particular plant cell

(E) to produce multiple effects on a particular subsystem of plant cells

Thank you. Much appreciated.

Posted from my mobile device

BrightOutlookJenn · Answer

Hi  oasis90

Yes, exactly.

The first paragraph is a good example of a process that you could decide to capture with a simple diagram with arrows. You could work backwards as follows:

You read:

You write:   express/turn on genes -> differentiate cells into roots, stems, etc

Then you read:

Then you write:   chem. mssgrs (hormones, reg. molecules)   before or above your existing notes, to represent their place in the process. 
So now your simple diagram says   "chem. mssgrs (hormones, reg. molecules) -> express/turn on genes -> differentiate cells into roots, stems, etc"

Then you read:

Now you write   5 maj. hormones + oligos. (new class)   under/over/next to the chem. messengers.
So your chain now says: 
  "chem. mssgrs (hormones, reg. molecules)   -> express/turn on genes -> differentiate cells into roots, stems, etc"

Now you've made a note/diagram that is  way clearer  than the words in the paragraph because it puts things in the right order and is more straightforward.

As we have seen before, any kind of a  process (A leads to B leads to C)  is important to notice when reading. GMAT loves to ask questions about these to see if we've really understood the process.

gmatconqueror2018 · Answer

I struggled to find the correct answers even after pausing the time and looking carefully into the passage. Probably the hardest passage anyone would encounter on the actual test. Never seen anything this complex before. Doesn't help that the answer choices sound very similar to one another as well.

ShukhratJon · Answer

Hi gmatconqueror2018,

Let me share my thoughts on this passage. I managed the passage in 09:08 and all my answers were correct. Initially, this type of passage was a nightmare of mine and I was in the same situation as you are in now. However, now I am doing pretty well on passages on anatomy and biology. What I did was to translate all the details of such passages and visualize the hormonal processes described in them. I googled hormones, enzymes, genes, chemical messengers, etc. and spent some time studying how they work. Pictures and videos about cells and their parts are easy to follow and memorize. Yes, all this took some time but it was both interesting and worth all the effort. Just translating and understanding are not enough. I also wanted to be able to visualize all the process described because thus I could easily memorize all new terms with their interrelation. As soon as I learnt a few passages this way, I became really comfortable with such passages. GMAT mostly uses the same terminology for such passages even if processes describes in them are different.

Actually, this tactic works well with passages in every topic. I read about feminism and especially about cosmos. Writings of Stephen Hopkins were really helpful. Vocabulary of his works seemed to be tough but I had to learn the terminology because I meet these words in RC a lot. On top, learning all new words I meet in RC is hugely helpful because thus I understand the passage fast, don’t have to read it twice, and memorize it easily so that I can answer questions without going back to it.

I hope I wrote at least something useful for you. Have a good day.

JDF · Answer

I have a real problem with the answer for 6.

OA is C. There is no acceptable definition of the word “artificial” that makes this answer choice correct.

Posted from my mobile device

ShukhratJon · Answer

Hi JDF,

You can find the correct answer for question 6 here:

Unlike the oligosaccharins, the five well-known plant hormones are pleiotropic rather than specific; that is, each has more than one effect on the growth and development of plants. The five has so many simultaneous effects that they are not very useful in artificially controlling the growth of crops.

This part of the passage says that  oligosaccharins are specific  while those five hormones are NOT specific but pleiotropic. Pleiotropic means that these five hormones don’t affect specific aspects of crops, but they have many different simultaneous effects (such as growing shoots, roots, vascular system, etc.). Because of pleiotropic nature, these five hormones cannot be used to  artificially  control the growth of the crop. We can infer that in order to  artificially  control the growth (growth is one of specific aspects of crop’s development) we need something SPECIFIC, namely  oligosaccharins . C exactly gives this answer.

Was it helpful?

Harsh2111s · Answer

Can someone explain question 2 ?

How option 'D" is the answer

GMATNinja · Answer

Question 2 
 
At the start of paragraph three, the passage says:

The pleiotropy of the five well-studied plant hormones  (a.k.a. the "five major hormones" identified in paragraph one)  is somewhat analogous to that of certain hormones in animal. For example, hormones from the hypothalamus in the brain stimulate the anterior lobe of the pituitary gland to synthesize and release many different hormones...

Paragraph four says:

Such a hierarchy may also exist in plants...There are indications that pleiotropic plant hormones  (again, these are the "five major hormones")  may actually function by activating the enzymes that release these other, more specific chemical messengers from the cell wall.

So, altogether, paragraphs three and four tell us that:

The pleiotropy of the pleiotropic hormones are  analogous  to certain animal hormones ( like hypothalamic hormones ). 
  Hypothalmic hormones exist in a hierarchy. Within that hierarchy, they stimulate a gland, which synthesizes and releases many different hormones, which then stimulate other glands and cause release of other hormones. 
  This kind of hierarchy may also exist in plants. The pleiotropic hormones occupy a similar space in this hierarchy as hypothalamic hormones in their hierarchy, because the pleiotropic hormones activate enzymes that then release other, more specific chemical messengers from the cell wall.

This is why (D) is the best answer choice. I hope this helps!

mSKR · Answer

Hi  GMATNinja   BrightOutlookJenn  , How to reject option E for Q3

Unlike the oligosaccharins, the five well-known plant hormones are pleiotropic rather than specific; that is, each has more than one effect on the growth and development of plants.

plant hormones has more than one effect on plants( systems- root, leave etc.) 
Unlike means:
O should have single effect on plants - multiple systems
or 
O should have multiple effect on a single subsystem

Hormones influence multiple sub-system . O influences single sub-system( can have single or mutiple effect)

How to come out of this confusion, with unlike , what is the right meaning?

IanStewart   MartyTargetTestPrep : Could you please help on this confusion.

Q3 and Q5 seem to be of too high level.

Thanks!

IanStewart · Answer

The text says: "Unlike the oligosaccharins, the five well-known plant hormones are pleiotropic rather than specific". So the five known hormones are pleiotropic, and the oligosaccharins are specific, and that's why they are unlike the five known hormones. The rest of the sentence just defines what 'pleiotropic' means.

I don't see how the text could be open to any other interpretation. I don't follow how you arrived at a potential distinction between "multiple systems" and "a single subsystem". Those phrases don't appear anywhere in the sentence using "unlike".

All of the cells in a particular plant start out with the same

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All of the cells in a particular plant start out with the same

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