In experiments in which certain kinds of bacteria were : GMAT Critical Reasoning (CR)
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# In experiments in which certain kinds of bacteria were

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In experiments in which certain kinds of bacteria were [#permalink]

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07 Oct 2006, 10:10
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In experiments in which certain kinds of bacteria were placed in a generous supply of nutrients, the populations of bacteria grew rapidly, and genetic mutations occurred at random in the populations. These experiments show that all genetic mutation is random.
Which one of the following, if true, enables the conclusion to be properly drawn?

A. Either all genetic mutations are random or none are random.

B. The bacteria tested in the experiments were of extremely common forms.

C. If all genetic mutations in bacteria are random, then all genetic mutations in every other life form are random also.

D. The kind of environment in which genetic mutation takes place has no effect on the way genetic mutation occurs.

E. The nutrients used were the same as those that nourish the bacteria in nature.
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07 Oct 2006, 10:39
Hallo,
The author generalizes about mutations in general from the example provided with bacteria. Then if C is true then the conclusion drawn must also be true
My ans is C)
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07 Oct 2006, 11:10
BG wrote:
Hallo,
The author generalizes about mutations in general from the example provided with bacteria. Then if C is true then the conclusion drawn must also be true
My ans is C)

That is EXACTLY what i thought and marked C. But the OA is not C.
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07 Oct 2006, 11:27
I also find C most appropriate.
A is just restating the conclusion. B looks irrelevant. D and E just show that the experiment did not create an environment different from that for the natural one.
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07 Oct 2006, 13:47

nothing ties the bacteria to other forms except this generalization
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07 Oct 2006, 13:57
Little confused between A and D

If A is true then even if one experiment shows that genetic mutations are random then all genetic mutations are random

D might be correct since it qualifies the experiment (an environment with high nutrients is specifically mentioned in the argument) if the environment were a factor then the argument falls apart..

I think A is more conclusive so leaning tow A
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07 Oct 2006, 15:08
mailtheguru wrote:
In experiments in which certain kinds of bacteria were placed in a generous supply of nutrients, the populations of bacteria grew rapidly, and genetic mutations occurred at random in the populations. These experiments show that all genetic mutation is random.
Which one of the following, if true, enables the conclusion to be properly drawn?

A. Either all genetic mutations are random or none are random.

B. The bacteria tested in the experiments were of extremely common forms.

C. If all genetic mutations in bacteria are random, then all genetic mutations in every other life form are random also.

D. The kind of environment in which genetic mutation takes place has no effect on the way genetic mutation occurs.

E. The nutrients used were the same as those that nourish the bacteria in nature.

This is D

In order to properly draw a conclusion we must prove that the conditions in the lab like the nutrients used , the ambient temp etc had no effect on the number of mutations that look place. D simply clears that up and enables us to draw the conclusion that "These experiments show that all genetic mutation is random".
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07 Oct 2006, 15:28
I'm going for D, holes in argument are we know nothing about variance of nutrients used or environment experiments done in, D clears this up.
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07 Oct 2006, 17:08
The OA is A
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07 Oct 2006, 17:26
I knew OA is A (1000cr) but not sure why.
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07 Oct 2006, 17:39
Juaz wrote:
I knew OA is A (1000cr) but not sure why.

I think A is more absolute. It gives only 2 possible choices all random or none random. since we observed in experiment random, we can conclude that all random.

D is good, because it takes care of environment factor, but what if there are some other factors that can prevent us from reaching conclusion that all are random.

for example I saw a white crow, so all crows are white.

A. says either all crows are white or none are white, so my conclusion is correct.
D. said on planet earth all crows are white. (but maybe there are some non-white crows in unknown planet)

what do you guys think?
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07 Oct 2006, 20:15
A is too extreme and unconvincing. The conclusion clearly states that "all genetic mutations are random," which is a very broad statement going well beyond the scope of just bacteria. Unless there is a misprint in the stimulus, I am still with (C) here.
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07 Oct 2006, 22:38
mailtheguru wrote:
In experiments in which certain kinds of bacteria were placed in a generous supply of nutrients, the populations of bacteria grew rapidly, and genetic mutations occurred at random in the populations. These experiments show that all genetic mutation is random.
Which one of the following, if true, enables the conclusion to be properly drawn?

A. Either all genetic mutations are random or none are random.

It's not about whether this answer choice is true or not in reality ....we're being tested about whether an argument is well established ...so there's nothing wrong with A.
The result of the experiment ensures the first half of A which, in turn, strengthens the conclusion.
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08 Oct 2006, 00:45
mailtheguru wrote:
In experiments in which certain kinds of bacteria were placed in a generous supply of nutrients, the populations of bacteria grew rapidly, and genetic mutations occurred at random in the populations. These experiments show that all genetic mutation is random.
Which one of the following, if true, enables the conclusion to be properly drawn?

A. Either all genetic mutations are random or none are random.

B. The bacteria tested in the experiments were of extremely common forms.

C. If all genetic mutations in bacteria are random, then all genetic mutations in every other life form are random also.

D. The kind of environment in which genetic mutation takes place has no effect on the way genetic mutation occurs.

E. The nutrients used were the same as those that nourish the bacteria in nature.

A has to be true to for the above conclusion to be true. As the evidence in the experiment proved that those mutations are random, now we can conclude (with support from A) that all the mutations are random. There is simply no chance of mutations being random during experiment, and other mutations being not random. A is a bullet proof statement.

If u go by statistics, B strengthens the conclusion. B says sample is representative. But sample need not exactly represent propulation. There B fails.

In C we are assuming that the sample represents the population accurately. That need not be the case. Experiment need not represent what happens usually in nature.

In D, we are ruling out what every scientist dreads, that environment in which the experiment is conducted is not influencing results. But what about the reliability of experimentation method itself? Can the experiments' results be applied to real world? D fails there. And A succeeds there.

E fails for the same reason as D. It is worried about the perfectness of the experiment, and not experiment as a representation of real world mutations.
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08 Oct 2006, 11:07
Very bizarre Q - but saying A...
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08 Oct 2006, 11:09
Very bizarre Q - but saying A...
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08 Oct 2006, 11:26
A

If it's an "all or none" scenario, and the mutations occurring in the populations are random, then it naturally follows that all genetic mutations are random.
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08 Oct 2006, 21:34
I picked C. Could anyone explain the difference between A and C?
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09 Oct 2006, 04:50
I accept A is correct.

C is not correct. The condition in C is "all genetic mutations in bacteria...", but the stimulus is just one example, not "all" mutations in bacteria. so C's logic does not hold.

A is closest then. C is a very deep trap.
09 Oct 2006, 04:50
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