Two genes BRCA1 and BRCA2 are linked to hereditary breast cancer. Therefore in order to decrease the annual number of mammogram tests administered across a population and to more accurately assess a woman's individual risk of breast cancer, all women should be tested for these genes.

Which of the following is the assumption?

A. Some women who are tested for the two genes will subsequently undergo mammograms on a less frequent basis than they used to.
B. The majority of breast cancer patients have no family history of the disease.
C. Researchers may have identified a third breast cancer gene that is linked with hereditary breast cancer.
D. Women who have these genes have an 80 pc chance of getting breast cancer while women who don't have these genes have only a 10 pc chance of getting breast cancer.
E. The presence of BRCA1 and BRCA 2 can explain upto to 50% of hereditary cases.



Answer is .

Think of NECESSARY assumption questions as eliminating roadblocks. You want to get from point A (the premises) to point B (the conclusion). You can't get there if there are roadblocks (things keeping you from reaching the conclusion). In other words it is NECESSARY to eliminate each roadblock if you want to get from A to B. Now if there are TWO roadblocks, it is necessary to eliminate roadblock 1 and roadblock 2 if you want to reach the conclusion, so either one of these could stand for a necessary assumption. So you look for the answer choice that eliminates roadblock 1, or if you can't find that, you look for the one that eliminates roadblock 2. You will NEVER see both of those as answer choices, because CR questions NEVER have two correct answers. Let me know if this doesn't help and i can go into a more in-depth discussion of the difference between NECESSARY and SUFFICIENT..

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Tim Sanders
Manhattan GMAT Instructor

Many thanks Tim... I meant to ask whether the correct answer should not deal with both the conditions aka the 'roadblocks'? - A just deals with one... i.e., reduction in frequency of testing. But A could not have been the full assumption as it doesn't deal with accuracy at all - so A is necessary but not sufficient on its own to be the 'complete assumption' - one that would account for both conditions - reduction of frequency of testing and accuracy

I was not thinking of separate answer choices dealing with each condition leading to a dilemma of picking 1 out of 2 choices

If there are two roadblocks, X and Y, and they ask what is necessary, you are looking for an answer choice that eliminates X, or Y, or both. Note that only one of these three will actually be an answer choice. If the questions is one of sufficiency, the correct answer choice will eliminate both X and Y. This is why it's important to consider exactly what is being asked. To answer your question more specifically, if they ask for an assumption that is necessary, you do not have to address all the issues the problem presents..

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Tim Sanders
Manhattan GMAT Instructor

Dear friends,

Why the ans D seems to me correct? If this is not correct then I want to tell you that that's how I always fall back i.e. run after lucrative wrong ans. I wan to kill them even they are of 700+ level pls give me the weaponry suggestion.

Tell me how did you kill them?

BR

Two genes BRCA1 and BRCA2 are linked to hereditary breast cancer. Therefore in order to decrease the annual number of mammogram tests administered across a population and to more accurately assess a woman's individual risk of breast cancer, all women should be tested for these genes.

Premise 1: 2 genes B1 and B2 are linked to heriditary Breast Cancer.

Conclusion :To decrease mamogram tests and to accurately assess a woman's risk, women should be tested for these genes.

We have to find Premise 2 or the assumption. This has to be something that links with Premise 1 in order to arrive at the conclusion.

Which of the following is the assumption?

A. Some women who are tested for the two genes will subsequently undergo mammograms on a less frequent basis than they used to.--This definitley proves that these tests are surely beneficial to some people in that they can reduce the number of mamographies that they have to undergo.Let's try and negate this assumption. What if, the frequencies of undergoing mamographies do not reduce even after women are tested for these 2 genes.Then our conclusion falls flat. ie; If sombody performs these tests, they will not undergo a reduction in the number of mamographies, let alone the accurate assessment of cancer, that is never stated. Hence our conlcusion collpases.Use this negation test to prove that this must be an assumption

B. The majority of breast cancer patients have no family history of the disease--So what if they had, what if they did not have; we need something that will connect the tests with more accurately assessing cancer and some information that helps us reduce mamogram tests.

C. Researchers may have identified a third breast cancer gene that is linked with hereditary breast cancer.--So how does this help in linking the new genes[B1 and B2] with the disease. If this assumption were to be true, then patients should also undergo a test for B3.This answer choice is mainly out of scope as it renders the Premise 1 ineffective.

D. Women who have these genes have an 80 pc chance of getting breast cancer while women who don't have these genes have only a 10 pc chance of getting breast cancer.--This might be what's called the trap answer. But let's look at our conclusion.Does this answer choice ever speak of how this would help in the reducing number of mamograms or does it ACCURATELY assess a woman's risk to breast cancer?The statistics merely provide a chance. What if these chances were to go against the odds. There is no way of definitely saying that it won't because it is a matter of probability and (P=1, we can be sure of some even to occur) there is no surety. Try the negation test here, and the conclusion will not fall apart, because the reduction in mamographies is never stated here and due to chance the patient might or might not have an accurate assessment in terms of treatment.

E. The presence of BRCA1 and BRCA 2 can explain upto to 50% of hereditary cases.--Let it explain 50, 60 or even 100% of hereditary cases. So what?Does it in anyway explain how this would reduce the number of mamograms?Or does it say, how this knowledge would accurately assess a woman's individual risk to breast cancer. No.

Hence, A is the best choice. --Hope this makes Sense!

My advice is to study the incorrect answer choices very thoroughly. Most students only check to see if they got the answer correct, then if it's incorrect they figure out why the incorrect answer is wrong. This leaves a lot of work undone on a given problem. Your goal should be to go through every single answer choice and make sure you thoroughly understand why all the wrong answer choices are wrong. The GMAT sets traps all over the place, and you have to train yourself to recognize those traps - especially the traps that look very appealing at first. Only then will you be able to spot these traps in future questions..

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Tim Sanders
Manhattan GMAT Instructor

I am slightly confused here..
Conclusion is ==> To decrease the annual number of mammogram tests administered across a population and to more accurately assess a woman's individual risk of breast cancer, all women should be tested for these genes.

Stripped down version of conclusion to match A ==> To decrease the annual number of mammogram tests administered across a population, all women should be tested for these genes.

I have 2 doubts:
1) Isn't A a subset/part of conclusion? A is just revolving in conclusion and need not to go to even premises to fill the gap and create so-called bridge, so how can we say that A is an assumption?
2) If we consider Y roadblock as "more accurately assess a woman's individual risk of breast cancer", then if D is considered true, we can say that majority of cases where breast cancer happens with two genes(80 %) can be tracked down and then cured for with the help of accurate assessment(Y). This looks fine. What would be reasoning for discarding D?

if A is the conclusion, then all the more reason for it to be the correct answer to an assumption question! the most useful assumption possible is one that assumes the conclusion is true. please note that this particular argument lends itself to all sorts of interpretations as to what the conclusion is, but if your interpretation is correct then A is by definition the best possible answer..

of course, that's also why we discard D - if A is the BEST POSSIBLE ANSWER, then by definition B, C, D, and E are not the correct answer..

_________________
Tim Sanders
Manhattan GMAT Instructor