Q16 - A common genetic mutation

[vik]

Let us negate Ans D. If there are some other people without the mutation who can still get periodontitis, then it cannot be eliminated simply by the new drug. Hence, Ans D must be correct. Where is my thinking flawed?

[pjohnso]

i believe your thinking is flawed b/c the stim doesn't say that the genetic mutation is the only way in which the enzyme is lowered and leads to gum diseases, but that it is simply common. for all we know, there are other, rarer ways to have a low amount of the enzyme, and they could get gum disease even if they did not have the mutation.

i struggled with this question b/c of answer choice A, however. i think i was thrown off b/c it says once the enzyme can be restored, we will be able to eliminate gum disease. to me, this implied that that was the only way to eliminate it. however, i guess the argument doesn't say anywhere that it is the only way, since there could be other treatments that don't involve the enzyme.

is answer choice correct b/c if they restored the enzyme to normal levels, and people still had gum disease, the argument isn't as strong? my thinking on eliminating e was that if they found a way to get everyone's enzyme level up, they could prevent any further cases of gum disease, though when they say eliminate it i can see how they would mean get rid of every case, which would depend on assuming e. ugh sorry for the confusing novel there, can anyone confirm/deny my thoughts though? thanks.

[noah]

Let's get to the core first of all:

Conclusion: Once a drug is developed to fix the enzyme levels, no more gum disease.

Why? (Premise): Because the enzyme levels helps protect the mouth.

The stuff about the genetic mutation is actually not central to the argument!

What's the gap? Well, could there be some gum disease even if your enzyme levels are OK? Maybe there's another way to get gum disease.

(E) address this gap - we have to assume that people who have taken this drug (and thus had their enzyme level fixed) will not get gum disease. Otherwise, how can we definitively conclude that gum disease will be eliminated from the premise given?

Negated: a person whose enzyme level is fixed might still get gum disease. That destroys the argument.

(A) is irrelevant. Even if there were other ways to stop gum disease (the negation of this answer choice), it still could be true that fixing the enzymes would end gum disease.

(B) is tempting if you thought the genetic mutation was important. But, in the end, even if there are other ways of getting low enzyme levels (negation of this answer choice), the drug should fix the levels.

(C) is out of scope - we're not talking about when things will happen.

(D) is similar to (B), though (D) links genetic mutation and gum disease while (B) just links genetic mutation and lowered enzyme levels. It's super tempting because you might think: Hey, there are folks out there who get gum disease from something other than these lowered enzyme levels, let's call it "eating sweets" - so even if they can fix the enzyme level, the folks who eat sweets will still get gum disease!

However, notice that (D) doesn't address whether gum disease can be caused by something other than the lowered enzyme levels. It addresses whether gum disease can be caused by something other than the mutation. If we negate (D) and have some non-mutated folks getting gum disease, perhaps the disease is still caused by having low enzyme levels. Perhaps, for example, eating sweets causes you to get low enzyme levels. If that's the case, no worries, the drug will take care of it!

That clear it up?

[skapur777]

I was confused here by the conclusion saying "we will be able to eliminate periodontitis."

By that I took it to me that they now have the potential to eliminate periodontitis.

If that is the case, how does the negation of E destroy the argument. A person whose cathepsin C level has been restored to normal MIGHT suffer from periodontitis.

That could be true, and the argument still holds. It's just now they have the prerequisite for eliminating periodontitis. Basically, it seems to me that I took normal cathepsin C levels as a necessary condition, rather than a sufficient condition for an elimination. How did you know that the conclusion instead stated that 'after raising enzyme to normal levels, no more gum disease'?

[noah]

First off, I was definitely paraphrasing when I said that the conclusion is "no more gum disease." You're right to be wary of such a move, though on balance such a "dumbing down" helps me digest and hold the argument core.

By that I took it to me that they now have the potential to eliminate periodontitis.

If that is the case, how does the negation of E destroy the argument. A person whose cathepsin C level has been restored to normal MIGHT suffer from periodontitis.

Even if we go with your more nuanced interpretation, how can we definitively conclude we can now eliminate gum disease if this drug will not deal with all the possible reasons to develop gum disease? Every conclusion has a "thus we can definitively say" implied.

Analogously: I can end famine, therefore I can end all international conflict.

Assumption: even with famine ended, there will not be another cause of international conflict.

How can I say that I definitely can end conflict if there may be a cause which my "cure" doesn't address?

Make sense?

[sbuzzetto10]

Don't know if this might also help, but--

The way I saw the flaw was:
a genetic mutation lowers this enzyme which reduces people's ability to ward off periodontitis
-once research allows us to restore the enzyme to normal levels, we will be able to eliminate periodontitis.
---nowhere in the premises does it say that having normal levels of the enzyme automatically means you won't get periodontitis, just that when you have lower levels, your ability to ward it off is reduced
*if the conclusion is going to work, it must be true that people with normal levels will not suffer from periodontitis (yes, E specifically says "restored to normal" but the assumption is still that normal=no periodontitis)

Hope that helps!

[msw99]

Okay, so I completely understand why E is correct but I'm still confused why D is incorrect.

I interpreted D as follows: if persons who do not have the genetic mutation can still get the gum disease then even with the new way to restore enzymes, periodontitis will not be eliminated because the new way has no impact on those persons with periodontitis orginating from something other than low enzymes.

Can someone please explain why D is incorrect? Thank you in advance!!

[noah]

I went back and edited my explanation of (D) to flesh it out a bit more. Tell me if that clears it up.

I believe the confusion is around whether (D) rules out enzyme levels as the cause of gum disease...it doesn't.

[msw99]

Helps a lot, thank you!

[seychelles1718]

Can someone please help me with my logic?

I picked E eventually but was seriously torn between A and E. The reason is that I thought the argument assumes lower level of enzyme causes periodontitis. I also believe the argument assumes lower enzyme is th only cause of gum disease because if there are other ways to get the disease, the conclusion that once enzyme level becomes normal, the disease will be eliminated does not hold. If lower enzyme level is the only cause of the disease, then the only way to eliminate the disease is to restore the enzyme level, which is what A is saying. In order to eliminate the effect( gum disease), we must eliminate the cause (lowet enzyme level).

Can someone please help me with my reasoning above?

[ohthatpatrick]

The author doesn't assume that lower C causes periodontitis, it explicitly says that "lower C severely reduces our ability to avoid periodontitis".

The author DOES definitely assume that the only way people get periodontitis is via low levels of C.

If there were OTHER ways to get periodontitis, his reasoning would be weakened. Even if we fix the "Low level of C" cause of periodontitis, we would not be "eliminating" periodontitis if there were other ways to get it.

He doesn't need to assume that raising levels of low C is the ONLY WAY to get rid of periodontitis.

His conclusion only demands that that raising levels of low C is a 100% SUCCESSFUL WAY to get rid of periodontitis.

CONSIDER THIS:
We're going to bet all our savings on a the biggest longshot horse at the Kentucky Derby. Once that horse wins, we will be rich.

Am I assuming, "Betting all our savings on the biggest longshot at the Derby is the only way to get rich"?

No, I'm not saying that's a NECESSARY way to get rich. I'm saying it's a SUFFICIENT way to get rich.

Where you're getting tangled is this:
"If lower enzyme level is the only cause of the disease, then the only way to eliminate the disease is to restore the enzyme level,

We don't know if "lower enzyme is the only cause of the disease".

As both of us said, the author is assuming that. But you're not allowed to make inferences based on their assumptions.

Get back to the Negation Test for Necessary Assumption. It always works. The correct answer, if negated, badly weakens the argument.

If we negate (A), it's saying "there's a different way to eliminate P".

Would that weaken? No. The author wasn't selling us on his way of eliminating P as the ONLY way. He was just saying it would be a 100% SUCCESSFUL way.

If we negate (E), it's saying "someone who's enzyme has been raised to normal MIGHT still suffer from P", it contradicts the sweeping certainty of the conclusion.

[WilliamS846]

so the argument is assuming that lower level of the enzyme is the only cause of gum disease ,but restoring the enzyme to normal level is not the only way to eliminate the gum disease. just like gaining weight is the only cause I may become unhappy but restoring weight to normal level is not the only way to eliminate my unhappiness. eating some chocolate may also make me happy(although I do suggest not doing so when you r overweight.lol)