PrepTest 124, Section 1, Question 3
Science columnist: It is clear why humans have(43 more words not shown)
Which one of the following,(21 more words not shown)
- ACats have built(13 more words not shown)
- BMost diseases that(10 more words not shown)
- CCats have more(9 more words not shown)
- DMany of the(13 more words not shown)
- EHumans have more(9 more words not shown)
Reading the argument
Similar genes could help explain similar diseases. But are these the diseases those genes cause?
The columnist tells us many human diseases have a genetic basis. We should accept that. The missing connection is between that general fact and the particular diseases humans share with cats. Those shared illnesses might instead have something to do with exposure to the same viruses or living in the same environment. Those are possibilities to consider, not facts the passage establishes.
There's another way to question the connection. Even if humans have counterparts to all the cat genes identified so far, humans could also have other genes. What if the genetically based human diseases involved those other genes? Then the genetic overlap wouldn't explain those diseases. Sharing some genetic material isn't enough; the relevant disease-causing material would have to overlap.
What we’re looking for
We're asked to weaken the explanation. I'd look for a reason the shared genes aren't doing the explanatory work the columnist assigns them. We can accept that cats and humans share diseases while questioning why they share them.
Working the answers
- A
Resistance concerns how cats respond to the diseases, not what causes those diseases. Cats could become resistant to illnesses that have a genetic basis. A doesn't show that the columnist has identified the wrong explanation for the overlap.
- BCorrect
Most of the diseases shared by cats and humans have no genetic basis. That directly challenges explaining the overlap through similar genes.
This is simpler than the possibility about disease-causing genes falling outside the shared genetic material. For most of these diseases, B removes the genetic basis altogether. We don't need to establish which virus or environmental factor actually causes them; showing that most aren't genetic is enough to weaken the proposed explanation.
Notice that this doesn't contradict the premise about many human diseases being genetic. Many human diseases can be genetic while most of the particular diseases shared with cats are not.
- C
The number of diseases cats share with other primates doesn't explain the cause of the diseases cats share with humans. Both overlaps could exist. We need evidence against the genetic explanation for this one, not a ranking of how many diseases different species share.
- D
Mild diseases still have causes, and an undiagnosed disease can still be genetically based. The severity and frequency of diagnosis don't settle whether shared genes explain the shared illnesses. D changes how noticeable the diseases are without challenging the proposed cause.
- E
This fits the passage's comparison: nonhuman primates are genetically closer to humans than cats are. It gives us no reason to doubt the proposed role of the genes humans do share with cats. Being closer to a third group doesn't eliminate the genetic overlap at issue.
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