parkhydel wrote:
In an attempt to produce a coffee plant that would yield beans containing no caffeine, the synthesis of a substance known to be integral to the initial stages of caffeine production was blocked either in the beans, in the leaves, or both. For those plants in which synthesis of the substance was blocked only in the leaves, the resulting beans contained no caffeine.
Any of the following, if true, would provide the basis for an explanation of the observed results EXCEPT:
A. In coffee plants, the substance is synthesized only in the leaves and then moves to the beans, where the initial stages of caffeine production take place.
B. In coffee plants, the last stage of caffeine production takes place in the beans using a compound that is produced only in the leaves by the substance.
C. In coffee plants, the initial stages of caffeine production take place only in the beans, but later stages depend on another substance that is synthesized only in the leaves and does not depend on the blocked substance.
D. In coffee plants, caffeine production takes place only in the leaves, but the caffeine then moves to the beans.
E. Caffeine was produced in the beans of the modified coffee plants, but all of it moved to the leaves, which normally produce their own caffeine.
CR00860.02
Passage Analysis In an attempt to produce a coffee plant that would yield beans containing no caffeine,
The purpose of an experiment is to produce a coffee plant that can provide coffee beans without the substance caffeine.
the synthesis of a substance known to be integral to the initial stages of caffeine production was blocked either in the beans, in the leaves, or both.
There is a substance that is vital in the first stage of producing caffeine. Let us call it X.
The making of this substance X was blocked in 3 sets of plants.
In one set it was blocked only in the beans, in the second only in the leaves and in the third set in both leaves and beans. For those plants in which synthesis of the substance was blocked only in the leaves, the resulting beans contained no caffeine.
We are given the result of only the set where the formation of X was blocked in leaves alone.
For them, the resulting beans contained no caffeine.
Question Stem Any of the following, if true, would provide the basis for an explanation of the observed results EXCEPT:
This is a paradox question of another type. Four of the choices are explanations that can be given to explain the result, but one is not. We need to identify the unsuitable explanation. Prethinking The loophole in this question is that we are not given the results of what happens when the substance X formation is blocked in just beans or both beans and leaves. All we know is that blocking X in the leaves leads to non-caffeinated beans. It could be possible that all three sets of plants gave non caffeinated beans, two of the sets gave non caffeinated beans (out of them, one is definitely ‘only leaves’ set) Or only one set gave non caffeinated beans (only leaves set). What we need to find is which of the given explanation does not provide and explanation for the ‘only leaves’ set giving non caffeinated beans.
Eg: 1. Complete production of caffeine happens in the beans and not the leaves. Then blocking X in “only leaves” should have no impact on caffeine production. This cannot explain the result.
2. Initial production of caffeine happens in the beans, and the leaves play a role only in a later part where the blocked substance has no role. If the blocked substance has no role at this stage of the caffeine creation process, then blocking X in “only leaves should have no impact on caffeine production. This cannot explain the result.
3. There are other parts of the coffee plant where the substance can be passed to the leaves where initial stages of caffeine production happens. Even if X formation is blocked in leaves, X can still be produced and reach the leaves for caffeine creation. Then blocking X in “only leaves” should have no impact on caffeine production. This cannot explain the result.
Option Analysis A. In coffee plants, the substance is synthesized only in the leaves and then moves to the beans, where the initial stages of caffeine production take place.
INCORRECT
If the substance X is synthesized only in the leaves and this production is blocked, then caffeine cannot be produced in the beans. Hence this is a correct explanation. Therefore, this cannot be the answer. B. In coffee plants, the last stage of caffeine production takes place in the beans using a compound that is produced only in the leaves by the substance.
INCORRECT
This option says in the last stage of production of caffeine, a substance produced by X is necessary, in the leaves. If X production in the leaves is blocked this cannot lead to caffeine production. Hence this is also a correct explanation and thus a wrong answer choice. C. In coffee plants, the initial stages of caffeine production take place only in the beans, but later stages depend on another substance that is synthesized only in the leaves and does not depend on the blocked substance.
CORRECT If initial stage of production takes place only in the beans, blocking X formation in leaves only has no impact. It is also mentioned that later stages do not depend on X. Thus, if this statement is true, it should not give the provided result. Hence this is the wrong explanation and thus the right answer choice. It is in line with explanation 2. D. In coffee plants, caffeine production takes place only in the leaves, but the caffeine then moves to the beans.
INCORRECT
If caffeine production takes place in the leaves, then blocking X can make an impact. Hence this is a proper explanation and an incorrect choice.
E. Caffeine was produced in the beans of the modified coffee plants, but all of it moved to the leaves, which normally produce their own caffeine.
INCORRECT
The option says that when the leaves were denied production of their own caffeine by blocking X formation, the caffeine that was formed in the beans all moved to the leaves, there by decaffeinating the beans. This is also a valid explanation for blocking X in the leaves leading to beans without caffeine. Hence it cannot be the correct answer choice.