In experiments in which certain kinds of bacteria were placed in a gen

Applied the process of elimination to get at this. The answer for this one would be quite simple for those who've studied science I suppose, because all that this question is trying to do is confuse you with its wording.




(A) Either all genetic mutations are random or none are random.
Correct answer.
The stem gives you information that the mutations occurred at random in the population. This statement is telling you that all genetic mutations either occur randomly, or none occur randomly. Putting two and two together gives us that since mutations occurred at random in the experiment, all mutations will always be random (which is the conclusion it wants us to arrive at).

(B) The bacteria tested in the experiments were of extremely common forms.
Not correct. If common forms of bacteria have mutations at random, how can we conclude that all mutations occur randomly?

(C) If all genetic mutations in bacteria are random, then all genetic mutations in every other life form are random also.
Not correct. This basically picks up the conclusion that we want to arrive at and uses it to further confuse the reader.

(D) The kind of environment in which genetic mutation takes place has no effect on the way genetic mutation occurs.
Not correct. Doesn't point us anywhere.

(E) The nutrients used were the same as those that nourish the bacteria in nature.
Not correct. Doesn't point us anywhere.

I think C basically bridges the gap b/w the conclusion and premise
Experts VeritasKarishma GMATNinja Bunuel please help??

These experiments show that all genetic mutation is random. (This is inclusive of Mutations in other organisms too)

We need to find which option best supports the claim (given the option is true).

A. Mutation is either random or specialized -> Mutation can have either of these two properties. Now with the experiment using one species we can confirm that the property is random.Once we know Mutation is random we know Mutation(-> property: random) applies to all species in general.
B. Mutation is true for common bacteria -> not applicable to all mutations in other organisms / even uncommon bacteria , excludes case of Mutation in other organisms
C. If true for bacteria then true for other organisms too -> not proper since correlation between bacteria and other lifeforms not stated
D. Kind of environment - no effect on mutation variability -> Within a single organism it is random and not dependent on environment type, but Mutation may depend on type of organism (some organisms instead of random mutation might see specialized mutations).
Species & Kind of environment - no effect on mutation variability , might make strong point.
E. Nutrient medium simulates natural environment - It proves that the exp. correctly simulates natural Mutation but not true for the generalized statement that can be made for other cases.

nightblade354
I did a blind review of this question, the original answer I selected was "C", but later on I changed it to "D".
What put me off in choice C was the use of "all" before " genetic mutations", the sentence does not quantify how much of genetic mutation occured randomly. I chose D as it hurts the argument directly, What if the environment(supply of nutrients) played some role; if it did then the conclusion would fall. Is there any flaw in my analysis? Did I assume the environment to be " supply of nutrients"?

This isn't an assumption question. This is a sufficienct assumption, which means that negation has no impact on it. Do not waste your time worrying about this because it will never show up on the GMAT.

OA from PowerScore Forum-

Here's how the argument sets up in very broad terms:

Premise: (some) genetic mutations in bacteria occurred at random.

Conclusion: all genetic mutation is random.
Second, from a mechanistic standpoint, the biggest change from premise to conclusion is the "some" and "all" elements. But, the conclusion contains the "all" element, so we need a way to get to that conclusion in the answer choices. Interestingly, only answer choices (A) and (C) reference the "all" element, so those two are the most attractive Contenders from the outset. Let's examine each answer more closely.

Answer choice (A): This is the correct answer. If we add this statement to the stimulus, we see an interesting structure. I'm going to remove the "genetic mutation" portion because that's common to all elements, and removing it allows us to isolate the numbers game being played:

(A): it's all or none.
Premise: it's some.
Conclusion: Well, since it's all or none, and the presence of some rules out none, it must be all.

That's literally the process at work here, and this answer choice allows us to connect the thread from "some" to "all" in the stimulus. However, and this is what makes this question a classic, they've made this connection in a very tricky fashion.

Answer choice (C): This answer choice can be diagrammed as:

All random in bacteria :arrow: all random in life
The problem here is that the sufficient condition, "All random in bacteria," isn't know (just "some" is known, which while it could be "all," isn't known to be "all" for sure) so adding this statement to the premises doesn't give us "all random in life" as the conclusion.

This answer can be analogized as follows:

(C): If all high school football players are athletic, then football players at every level of the sport are athletic
Premise: Some high school football players are athletic.
Conclusion: No conclusion can be drawn.