Researchers studying the spread of the Black Plague in sixteenth-centu

Question

Researchers studying the spread of the Black Plague in sixteenth-century England claim that certain people survived the epidemic because they carried a genetic mutation, known as Delta-32, that is known to prevent the bacteria that causes the Plague from overtaking the immune system. To support this hypothesis, the researchers tested the direct descendants of the residents of an English town where an unusually large proportion of people survived the Plague. More than half of these descendants tested positive for the mutation Delta-32, a figure nearly three times higher than that found in other locations.

The researchers' hypothesis is based on which of the following assumptions?

(A) Delta-32 does not prevent a carrier from contracting any disease other than the Plague.

(B) The Plague is not similar to other diseases caused by bacteria.

(C) Delta-32 did not exist in its current form until the sixteenth century.

(D) No one who tested positive for Delta-32 has ever contracted a disease caused by bacteria.

(E) The Plague does not cause genetic mutations such as Delta-32.

This question is part of the  GMAT Club Critical Reasoning : Assumption" Revision Project.

Bunuel · Accepted Answer

OFFICIAL EXPLANATION

The researchers claim that Delta-32 prevents its carriers from contracting the Plague. They support this claim by noting that a strikingly large percentage of descendants of Plague survivors carry the mutation. We are asked to find an assumption underlying the claim.

(A) The argument is specific to the relationship between Delta-32 and resistance to the Plague. Other diseases are irrelevant.

(B) Again, the argument is specific to the relationship between Delta-32 and resistance to the Plague. Other diseases are irrelevant.

(C) Delta-32 may have existed in its current form before the sixteenth century and the merit of the argument would not change.

(D) The argument does not claim that Delta-32 prevents all bacteria-caused disease.

(E) CORRECT . The researchers claim that Delta-32 prevented its carriers from contracting the Plague on the basis of its presence in descendants of Plague survivors. But it is theoretically possible that these descendants carry the mutation Delta-32 because the Plague mutated the genes of their ancestors. In order to claim that the mutation prevented the Plague, we must assume that the Plague did not cause the mutation Delta-32.

shrouded1 · Answer

onedayill · Answer

This is cause and effect type of question. 
E shows that reverse is not possible. 
Therefore, E is correct.

adishail · Answer

Irrelevant a) Delta-32 does not prevent a carrier from contracting any disease other than the Plague. Irrelevant b) The Plague is not similar to other diseases caused by bacteria. Again, irrelevant :roll:

c)Delta-32 did not exist in its current form until the sixteenth century. Again, irrelevant :roll:

d)No one who tested positive for Delta-32 has ever contracted a disease caused by bacteria. They assumed this to be true, else this would have been a side affect and not the reason to survive the plague. In order for Delta-32 to be the reason of surviving, it had to be present before the plague spread and was not a result of exposure to the bacteria e)The Plague does not cause genetic mutations such as Delta-32.

ChrisLele · Answer

Fun question!

One good way to attack the question is by negating the assumption. If we do so with (E) we get:

Negated Answer Choice: The Plague causes genetic mutations such as Delta-32.

If the Plague indeed caused Delta-32 to occur, then the researches hypothesis totally falls apart: Delta-32 did not protect against the plague.

Answer choice (C) says that Delta-32 came into being around the 16th century, about the time of the Plague. Therefore, it could have conceivably conferred immunity on those who carried the gene.

Hope that helps

.

Dipankar6435 · Answer

Got this question on one of MGMAT CATs. Even after reviewing the problem and reading some posts regarding this I can still not convince myself that E can be the right answer. Here is my submission regarding it - To support this hypothesis, the researchers tested the direct descendants of the residents of an English town where an unusually large proportion of people survived the Plague . More than half of these descendants tested positive for the mutation Delta-32, a figure nearly three times higher than that found in other locations. As highlighted these two parts in the argument tell us two things 1. This town had an unusually large number of people who survived the Plague. 2. More than half of the descendants tested positive for DElta-32 in this town, a number three times as high as other locations Now E says - The Plague does not cause genetic mutations such as Delta-32. This cannot be assumed as per the argument. Had plague caused the mutations the proportion of people having Delta-32 would have been much higher in other locations where the plague was much more widespread than in this town which had fewer instances of plague. In fact in this question I feel no answer is correct. Can some experts enlighten me on this :shock:

plumber250 · Answer

Hi dipankar,

The key thing you need to think about is the difference between the number of people who contracted the plague and the number of people who survived it.

The question talks about people who survive it, whilst you talk about numb of people who contract it.

Re-look in this light and it should be clearer....

chshashankreddy · Answer

Researchers studying the spread of the Black Plague in sixteenth-century England claim that certain people survived the epidemic because they carried a genetic mutation, known as Delta-32, that is known to prevent the bacteria that causes the Plague from overtaking the immune system. To support this hypothesis, the researchers tested the direct descendants of the residents of an English town where an unusually large proportion of people survived the Plague. More than half of these descendants tested positive for the mutation Delta-32, a figure nearly three times higher than that found in other locations.

The researchers' hypothesis is based on which of the following assumptions?
 a) Delta-32 does not prevent a carrier from contracting any disease other than the Plague.
 b) The Plague is not similar to other diseases caused by bacteria.
 c)Delta-32 did not exist in its current form until the sixteenth century.
 d)No one who tested positive for Delta-32 has ever contracted a disease caused by bacteria.
 e)The Plague does not cause genetic mutations such as Delta-32

Conclusion: People survived the plague because they carried a genetic mutation Delta 32.

Negating each option, E stands out to break the conclusion.

-E = The plague causes the genetic mutation such as Delta 32. If the plague itself causes the mutation than all the people effected by the plague will possess the mutation which is the explanation for the premise provided.

Hence E.

AryamaDuttaSaikia · Answer

The argument states that the mutated Delta-32 gene acted as a defense against the bacteria causing Black Plague. The descendants tested from the English town where most of the people did not have the disease provides additional evidence to the above claim. The author assumes that the gene was already in the mutated form and the mutation could not have been a result of the disease. "E" rightly identifies the assumption. If "E" is reversed that is Plague caused the mutation then in the reversed form "E" attacks the conclusion.

DeepikaV · Answer

Hi,

please explain why D is wrong in detail.

KarishmaB · Answer

Premises:

Researchers claim that certain people survived the epidemic because they carried Delta-32 which prevents Plague.
They tested the direct descendants of the residents of an English town where an unusually large proportion of people survived the Plague. 
More than half of these descendants tested positive for the mutation Delta-32, a figure nearly three times higher than that found in other locations.

What is the assumption? A missing necessary premise?

• No one who tested positive for Delta-32 has ever contracted a disease caused by bacteria.

We are not assuming that people carrying Delta-32 can get no bacterial infection. All that the argument says is that Delta-32 prevents plague. It may be ineffective against other bacteria. We don't need to assume its effectiveness against all bacteria for our argument to hold.

• The Plague does not cause genetic mutations such as Delta-32.

The higher proportion of Delta-32 in that town could be explained in two ways:
- They had Delta-32 and hence did not get plague. If more people had Delta-32, it means more people would have survived.
- Their system resisted plague and that led to the mutation. If more people resisted and survived, it would mean more mutation.

By concluding that first case must have taken place, we are assuming that second did not. So that is why (E) is an assumption.

BillyZ · Answer

Let’s review the two roles played by assumptions:

Supporter Assumption : These assumptions link together new or rogue elements in the stimulus or fill logical gaps in the argument.

Defender Assumption : These assumptions contain statements that eliminate ideas or assertions that would undermine the conclusion. In this sense, they “defend” the argument by showing that a possible source of attack has been eliminated.

Three Quirks of Assumption Question Answer Choices

Over the years, certain recurring traits have appeared in Assumption answer choices. Recognizing these quirks may help you eliminate wrong answers or more quickly identify the 
correct answer at crunch time.

1. Watch for answers starting with the phrase “ at least one ” or “ at least some .”

For some reason, when an Assumption answer choice starts with either of the above constructions the chances are unusually high that  the answer will be correct . However, if you spot an answer with that construction, do not simply assume the answer is correct; instead, use the  proper negation  (“ None ”) and check the answer with the Assumption Negation Technique.

2. Avoid answers that claim an idea was the most important consideration for the author.

These answers typically use constructions such as “the primary purpose,” “the top priority,” or “the main factor.” In every Assumption question these answers have been wrong. And, unless, the author specifically discusses the prioritization of ideas in the stimulus, these answers will continue to be wrong because an author can always claim that the idea under discussion was very important but not necessarily the most important idea.

3. Watch for the use of “ not ” or negatives in assumption answer choices.

Because most students are conditioned to think of assumptions as positive connecting elements, the appearance of a negative in an Assumption answer choice often causes the answer to be classified a Loser. Do not rule out a negative answer choice just because you are used to seeing assumptions as a positive part of the argument. As we have seen with Defender answer choices, one role an assumption can play is to eliminate ideas that could attack the argument. To do so, Defender answer choices frequently contain negative terms such as “ no ,” “ not ,” and “ never .” One benefit of this negative language is that Defender answer choices can usually be negated quite easily.

Assumptions and Causality

“When a GMAT speaker concludes that one occurrence caused another, that speaker also assumes that the stated cause is the  only possible cause  of the effect and that the stated cause will always produce the effect.”

Thus, because the author always assumes that  the stated cause is the only cause , Assumption answer choices tend to work exactly like Strengthen answer choices in arguments with causal reasoning. The correct answer to an Assumption question will normally fit one of the following categories:

A. Eliminates an alternate cause for the stated effect

Because the author believes there is  only one cause  (the stated cause in the argument),  the author assumes no other cause exists .

B. Shows that when the cause occurs, the effect occurs

Because the author believes that the cause always produces the effect, assumption answers will affirm this relationship.

C. Shows that when the cause does not occur, the effect does not occur

Using the reasoning in the previous point, the author will always assume that when the cause does not occur, the effect will not occur.

D. Eliminates the possibility that the stated relationship is reversed

Because the author believes that the cause-and-effect relationship is correctly stated, the author assumes that the relationship cannot be backwards (the claimed effect is actually the cause of the claimed cause).

E. Shows that the data used to make the causal statement are accurate, or eliminates possible problems with the data

If the data used to make a causal statement are in error, then the validity of the causal claim is in question. The author assumes that this cannot be the case and that the data are accurate.

JuccGMAT · Answer

Conclusion:-certain people survived the epidemic because they carried a genetic mutation

We are looking for the information that states that those certain people really carried that genetic mutation. In other words, there shouldn't be any other way from which this mutation developed .

Choice E is the prefect match.

krndatta · Answer

KarishmaB  Ma'am,

The negation of option E is "The plague causes the Delta-32 mutation" This weakens the conclusion that Delta-32 was responsible for preventing the spread of plague because the plague itself was causing the Delta-32 mutation.

Please evaluate my reasoning.

KarishmaB · Answer

Yes, you seem to have it right. 
Though just to be sure, let me point out that because scientists found that unusually large number of survivors in a town correspond with unusually large number of people with Delta-32 mutation, they concluded that Delta-32 helped in fighting plague. 
But what if Delta-32 was caused by plague. That could also explain the unusually large number of people with both. Then also a town with unusually large number of survivors (people who caught the plague but did not die) will have unusually large number of Delta-32 mutations. 
Option (E) says that plague does not cause Delta-32. So it negates a possible alternative explanation for the situation. To conclude that Delta-32 helps fight plague, we are assuming that no other alternative explanation works (so we are assuming that Delta-32 was not caused by plague).
Hence (E) is correct.

shvm_sin7 · Answer

I did not quite understand, the surrvivors wre technically 'not infected' because their immune system protected them. Therefore negating the argument (E) should not cause an problems acc to me

Researchers studying the spread of the Black Plague in sixteenth-centu

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