Even without the limitations imposed by the expense and difficulty of

Question

Even without the limitations imposed by the expense and difficulty of simply creating transgenic organisms, organisms with altered copies of one or more genes, the process of genetically engineering organisms for specific phenotypes – physical characteristics rather than genetic ones – can be fraught with difficulties. To a student of traditional Mendelian genetics, however, this may not be self-evident. After all, if one can find the gene that governs a specific trait and isolate it, then it should behave the way in another organism of the same type.

But despite the optimism suggested by Mendelian genetics, in practice the process is incredibly difficult, even if you are only interested in copying genes from another member of the same species. This is because even two genetically identical individuals may not develop in an identical manner if grown in different environments – or even in the same one. For example, the first cloned cat was cloned from a calico, but did not share the distinct orange and black splotching characteristic of its “mother.” It was instead a tiger-striped, grey cat, with no orange on it at all despite the fact that the two cats were genetically identical. The difference in appearance was due to a phenomenon known as X-inactivation, a phenomenon that occurs in female mammals in which one of the two copies of the X-chromosome in each cell is randomly “switched off” during embryonic development. The embryo then develops as a sort of mosaic – some cells exhibit one form of the X-chromosome, and others the other. Since fur color is held on the X-chromosome, two female cats can look nothing like one another even if they are genetically identical.

Processes like X-chromosome inactivation mean that researchers must test transgenic organisms carefully to ensure that there are no unintended consequences from the creation of transgenic or cloned organisms. Additionally, they must test to ensure that, in different environments, the cloned genes act as intended. In the absence of such testing, millions of dollars and thousands of hours of researchers’ time could be lost in producing organisms that have little to no value relative to their intended purpose.   1  1. Which of the following can be correctly inferred from the passage?

A. Unintended consequences from creating transgenic organisms are only a concern when dealing with female mammals
 
B. X-inactivation is not described under Mendelian genetics.
 
C. Researchers can avoid unintended consequences by ensuring that they are dealing with similar organisms.
 
D. The monetary drawbacks of problems arising from transgenic organisms outweigh the benefits.
 
E. Cloned organisms usually develop differently than their “parents” due to X-inactivation

OE:  This specific inference question requires that you be able to determine which answer choice is guaranteed from the passage but isn’t directly stated. Remember that, as with any specific question, you must be able to support your inference with data from the passage. If there’s no support, then the answer choice must be incorrect. Since there is no information in the question stem about where in the passage you should look back, use your answers as assets and look to your answer choices to guide your reading.

Choice (A) claims that unintended consequences with transgenic organisms are only an issue with female mammals. While the second paragraph does go into great detail about the issues of a particular cloned female mammal, it neither claims nor implies that this problem is exclusive to female mammals. Choice (A) can therefore be eliminated.

Choice (B) states that X-inactivation isn’t covered under Mendelian genetics. This is indeed implied by the passage. The end of the first and beginning of the second paragraph state that Mendelian genetics predicts that genes will behave in certain ways. Since X-inactivation is said to violate those rules, it must not be covered under the Mendelian system. Choice (B) is therefore correct.

Choice (C) claims that researchers can avoid unintended consequences by dealing with similar organisms. The second paragraph directly contradicts this by comparing two genetically identical organisms where unintended consequences were seen, so choice (C) can be eliminated.

Choice (D) makes a value judgment on the costs and benefits of creating transgenic organisms. Because the author discusses costs but makes no mention of benefits – or lack of benefits – this is a conclusion that cannot be drawn from the text.

Choice (E) claims that cloned organisms usually develop differently from their “parents”. However, while one case of this phenomenon is discussed, there is no discussion as to whether this is the exception or the rule.

2 2. Which of the following experiments, if carried out, would best test one of the issues mentioned in paragraph 3?

A. Two cloned organisms are raised in different environments and monitored for differences in phenotype.
 
B. Two transgenic organisms with the same genotype are raised in the same environment.
 
C. An organism without a specific gene modification is compared to one that does have the modification.
 
D. Two organisms with different cloned genes are monitored for differences in their phenotypes

E. An organism with a cloned gene is monitored to see how efficiently the cloned gene performs.

OE:  This question requires that you first understand the problem posed in paragraph three and then decide which test would best mitigate this concern. Paragraph three talk about the fact that it is important for researchers to determine that there are no unintended consequences from the creation of transgenic organisms or to determine that the cloned genes act as intended across different environments.

Choice (A) is correct: it looks at two identical organisms in different environments. If they are monitored for differences in phenotype – defined earlier in the passage as physical traits – then that also covers the requirement that scientists determine that cloned genes “act as intended” in different environments.

Choice (B) also deals with a copied gene, but can be eliminated because the organisms are observed in the same environment.

Choice (C) might allow researchers to look at how the gene acts in the new organism, but it doesn’t account for how the genes perform in different environments and can therefore be eliminated.

Choice (D) doesn’t allow for comparison of the same gene across different environments, so it can be eliminated.

Choice (E) doesn’t allow for either comparison between organisms or across different environments and can be eliminated.

Notice that while the language in the answer choices might seem technical that this question mostly required that you match a few pieces of information – the ideas of comparison and different environments – rather than synthesize massive amounts of information.

3 3. Why does the author use quotes around the term "mother" in the second paragraph?

A. To highlight the fact that X-inactivation occurs in females.
 
B. To explain the relationship between the two cats in the example.
 
C. To signify the importance of the term "mother" to the reader.
 
D. To indicate that the term is more of a metaphor than as an exact relationship.
 
E. To emphasize that the two cats, despite their relationship, look completely different.
OE:  In this Function question, you're asked why the author uses quotes around the term "mother" in the second paragraph. In that portion, the author is talking about the two cats in the example, one of which is cloned from the other.

Importantly you're asked why the author uses the quotes around the term, and not why the author uses the term itself. Choice (B) might be tempting, as the purpose of that sentence is to help establish the relationship between the cats. But the author uses the quotes for another reason - is the organism from which a clone receives its DNA structure truly its mother? Choice (D) hits the exact reason that the author uses the quotes, to demonstrate that the original calico cat isn't truly the "mother" but rather the original owner of the DNA template for the second cat. The quotes serve to show that the term "mother" is a metaphor and not a true, biological relationship.

Note that choices (A) and (E) each occur within that paragraph (the author does note that X-inactivation occurs in females, and emphasizes that the cats look different) but neither is the reason for that specific use of quotes. Remember: in a Function question, it is critical to answer the exact question that you are asked.

Choice (D) is correct.

4  4. Which of the following can be inferred from the passage?

A. If two genetically-identical organisms exhibit different physical traits, those differences are a result of X-inactiviation.

B. Because of X-inactivation, no two organisms are ever truly genetically identical.

C. X-inactivation occurs more frequently in calico cats than in other mammals.

D. Not all pairs of genetically identical organisms are physically identical.

E. When identical twins exhibit different phenotypes, the differences more often result from having developed in different environments than from X-inactivation.

OE:  In any Inference question, the correct answer must be true, meaning that it must be proven by information in the passage. If you cannot find proof for an answer, then it is not necessarily true and therefore incorrect.

For this question, answer choice (D) must be true: the second paragraph includes direct proof with the line "two genetically identical individuals may not develop in an identical manner," as well as the example of the two genetically-identical cats that look completely different. Because of this you can conclude that not all pairs of genetically identical organisms are physically identical.

Among the other choices:

(A) can be disproven at the beginning of paragraph two with the line "two genetically identical individuals may not develop in an identical manner if grown in different environments." This suggests that environment can result in differences, showing that X-inactivation is not the only cause.

(B) cannot be proven, as you're even told toward the end of paragraph two that X-inactivation occurs "in female mammals." Since female mammals are not the only organisms, you should see that X-inactivation cannot affect all pairs of genetically-identical organisms.

(C) has no proof anywhere in the passage: you're given one example about calico cats, but not given any information about how often X-inactivation occurs in that population vs. others.

And (E) seems like it should be true (and were you to study genetics you would see that it is), but from the passage itself you aren't given a comparison of how often differences result from each factor. This choice simply goes too far beyond the scope of what is given in the passage, and is incorrect.

gmat1393 · Answer

Hi  workout

Can you add the OA as  B  for the first question and please help in understanding why the OA is  D  for third question.Its not clear even after seeing the OE.

Thanks!

Nikhil · Answer

Thanks  gmat1393

For question 3, even though I got it wrong, I agree with the OE provided. Read the following lines again.

"Choice (D) hits the exact reason that the author uses the quotes, to demonstrate that the original calico cat isn't truly the "mother" but rather the original owner of the DNA template for the second cat."

Which part of OE you don't understand? Let me know.

arvind910619 · Answer

Please explain question 2 .
As per my understanding A and B both can be answers. 
Please give OE

Nikhil · Answer

1. Which of the following can be correctly inferred from the passage?

This specific inference question requires that you be able to determine which answer choice is guaranteed from the passage but isn’t directly stated. Remember that, as with any specific question, you must be able to support your inference with data from the passage. If there’s no support, then the answer choice must be incorrect. Since there is no information in the question stem about where in the passage you should look back, use your answers as assets and look to your answer choices to guide your reading.

A. Unintended consequences from creating transgenic organisms are only a concern when dealing with female mammals

INCORRECT  Choice (A) claims that unintended consequences with transgenic organisms are only an issue with female mammals. While the second paragraph does go into great detail about the issues of a particular cloned female mammal, it neither claims nor implies that this problem is exclusive to female mammals. Choice (A) can therefore be eliminated.
 
 B. X-inactivation is not described under Mendelian genetics.

Correct  Choice (B) states that X-inactivation isn’t covered under Mendelian genetics. This is indeed implied by the passage. The end of the first and beginning of the second paragraph state that Mendelian genetics predicts that genes will behave in certain ways. Since X-inactivation is said to violate those rules, it must not be covered under the Mendelian system. Choice (B) is therefore correct.

C. Researchers can avoid unintended consequences by ensuring that they are dealing with similar organisms.

INCORRECT  Choice (C) claims that researchers can avoid unintended consequences by dealing with similar organisms. The second paragraph directly contradicts this by comparing two genetically identical organisms where unintended consequences were seen, so choice (C) can be eliminated.
 
 D. The monetary drawbacks of problems arising from transgenic organisms outweigh the benefits.

INCORRECT  Choice (D) makes a value judgment on the costs and benefits of creating transgenic organisms. Because the author discusses costs but makes no mention of benefits – or lack of benefits – this is a conclusion that cannot be drawn from the text.
 
 E. Cloned organisms usually develop differently than their “parents” due to X-inactivation

INCORRECT  Choice (E) claims that cloned organisms usually develop differently from their “parents”. However, while one case of this phenomenon is discussed, there is no discussion as to whether this is the exception or the rule.

2. Which of the following experiments, if carried out, would best test one of the issues mentioned in paragraph 3?

This question requires that you first understand the problem posed in paragraph three and then decide which test would best mitigate this concern. Paragraph three talk about the fact that it is important for researchers to determine that there are no unintended consequences from the creation of transgenic organisms or to determine that the cloned genes act as intended across different environments.

A. Two cloned organisms are raised in different environments and monitored for differences in phenotype. 
 
 Correct  Choice (A) is correct: it looks at two identical organisms in different environments. If they are monitored for differences in phenotype – defined earlier in the passage as physical traits – then that also covers the requirement that scientists determine that cloned genes “act as intended” in different environments.

B. Two transgenic organisms with the same genotype are raised in the same environment.

INCORRECT  Choice (B) also deals with a copied gene, but can be eliminated because the organisms are observed in the same environment.
 
 C. An organism without a specific gene modification is compared to one that does have the modification.

INCORRECT  Choice (C) might allow researchers to look at how the gene acts in the new organism, but it doesn’t account for how the genes perform in different environments and can therefore be eliminated.
 
 D. Two organisms with different cloned genes are monitored for differences in their phenotypes

INCORRECT  Choice (D) doesn’t allow for comparison of the same gene across different environments, so it can be eliminated.

E. An organism with a cloned gene is monitored to see how efficiently the cloned gene performs.

INCORRECT  Choice (E) doesn’t allow for either comparison between organisms or across different environments and can be eliminated.

Notice that while the language in the answer choices might seem technical that this question mostly required that you match a few pieces of information – the ideas of comparison and different environments – rather than synthesize massive amounts of information.

3. Why does the author use quotes around the term "mother" in the second paragraph?

A. To highlight the fact that X-inactivation occurs in females.
 
B. To explain the relationship between the two cats in the example.
 
C. To signify the importance of the term "mother" to the reader.
 
D. To indicate that the term is more of a metaphor than as an exact relationship.
 
E. To emphasize that the two cats, despite their relationship, look completely different.

In this Function question, you're asked why the author uses quotes around the term "mother" in the second paragraph. In that portion, the author is talking about the two cats in the example, one of which is cloned from the other.

Importantly you're asked why the author uses the quotes around the term, and not why the author uses the term itself. Choice (B) might be tempting, as the purpose of that sentence is to help establish the relationship between the cats. But the author uses the quotes for another reason - is the organism from which a clone receives its DNA structure truly its mother? Choice (D) hits the exact reason that the author uses the quotes, to demonstrate that the original calico cat isn't truly the "mother" but rather the original owner of the DNA template for the second cat. The quotes serve to show that the term "mother" is a metaphor and not a true, biological relationship.

Note that choices (A) and (E) each occur within that paragraph (the author does note that X-inactivation occurs in females, and emphasizes that the cats look different) but neither is the reason for that specific use of quotes. Remember: in a Function question, it is critical to answer the exact question that you are asked.

Choice (D) is correct.

4. Which of the following can be inferred from the passage?

A. If two genetically-identical organisms exhibit different physical traits, those differences are a result of X-inactiviation.

B. Because of X-inactivation, no two organisms are ever truly genetically identical.

C. X-inactivation occurs more frequently in calico cats than in other mammals.

D. Not all pairs of genetically identical organisms are physically identical.

E. When identical twins exhibit different phenotypes, the differences more often result from having developed in different environments than from X-inactivation.

In any Inference question, the correct answer must be true, meaning that it must be proven by information in the passage. If you cannot find proof for an answer, then it is not necessarily true and therefore incorrect.

For this question, answer choice (D) must be true: the second paragraph includes direct proof with the line "two genetically identical individuals may not develop in an identical manner," as well as the example of the two genetically-identical cats that look completely different. Because of this you can conclude that not all pairs of genetically identical organisms are physically identical.

Among the other choices:

(A) can be disproven at the beginning of paragraph two with the line "two genetically identical individuals may not develop in an identical manner if grown in different environments." This suggests that environment can result in differences, showing that X-inactivation is not the only cause.

(B) cannot be proven, as you're even told toward the end of paragraph two that X-inactivation occurs "in female mammals." Since female mammals are not the only organisms, you should see that X-inactivation cannot affect all pairs of genetically-identical organisms.

(C) has no proof anywhere in the passage: you're given one example about calico cats, but not given any information about how often X-inactivation occurs in that population vs. others.

And (E) seems like it should be true (and were you to study genetics you would see that it is), but from the passage itself you aren't given a comparison of how often differences result from each factor. This choice simply goes too far beyond the scope of what is given in the passage, and is incorrect.

gmat1393 · Answer

Hi  workout

Since 2 para implies that even two related genes may have different characteristics. I selected option E.

Nikhil · Answer

The question is regarding the usage of "quotes" around the word mother and not the word mother itself. So, Option D makes much more sense than option E.

arora1 · Answer

so many inference questions :/

OJA · Answer

KarishmaB   Sajjad1994  - Can you please help me with Q2? I am confused as to what really is the focus of the question? So my understanding is there are 2 things that is suggested for further research. 1. "carefully to ensure that there are no unintended consequences from the creation of transgenic or cloned organisms." And 2. "Additionally, they must test to ensure that, in different environments, the cloned genes act as intended."

In that case, most of the options seems to make sense to me. So for example -

A. Two cloned organisms are raised in different environments and monitored for differences in phenotype. - ofcourse, this makes sense.

C. An organism without a specific gene modification is compared to one that does have the modification. - Wouldn't this be relevant for 1.So if we compare the one with the modification and one without, this would help us understand for any unintended consequences.

E. An organism with a cloned gene is monitored to see how efficiently the cloned gene performs. - Same goes for this option. If we are monitoring their development, this would also help us to understand for any unintended consequences.

Could you please help?

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