PrepTest 106, Section 2, Question 21
Wirth: All efforts to identify a gene responsible(83 more words not shown)
The point at issue between(5 more words not shown)
- Aefforts to identify(16 more words not shown)
- Bit is likely(16 more words not shown)
- Cnearly all researchers(8 more words not shown)
- Dcurrent research supports(10 more words not shown)
- Ethe efforts made(13 more words not shown)
Reading the argument
We haven't found the gene. Does that mean there isn't one, or could we have been looking in the wrong place? That's my first reaction to Wirth's evidence. A failed search doesn't automatically settle what exists.
But Wirth goes further: even if the researchers are right that there is no single gene, nobody can be genetically predisposed to manic-depression. Why couldn't several genes work together? Ruling out one gene that does the job alone wouldn't rule out an effect produced by a combination.
Chang raises exactly that objection. Chang accepts the evidence about the single gene and points to research supporting interactions among several genes. I'm on Chang's side here. Wirth has treated one possible genetic explanation as though it were the only possible genetic explanation.
What we’re looking for
The question asks where they disagree. Keep the answer at the level of Wirth's conclusion: does this research support saying there is no genetic predisposition? Wirth says yes. Chang says no, because the evidence for several genes leaves a genetic explanation available. We don't need a dispute about whether the search for a single gene failed.
Working the answers
- A
Be careful: this includes both a single gene and a set of genes. Chang reports evidence for a set, so Chang would reject the claim that every effort described here failed. But Wirth's evidence specifically concerns the search for a single gene. Wirth doesn't separately report that every search for a set failed. We can't establish both speakers' positions on this broader statement just by extending Wirth's evidence. Their explicit clash is over the conclusion about genetic predisposition.
- B
Neither speaker makes this prediction about future research. Chang's objection doesn't require believing that researchers will eventually find one gene. Several genes could explain the predisposition even if a single-gene explanation never succeeds.
- C
This is part of Wirth's evidence, and Chang explicitly accepts that evidence. The researchers could agree that there is no single manic-depression gene while finding evidence that several genes interact. Those findings can coexist; they aren't the disagreement.
- DCorrect
Wirth takes the research to support the claim that nobody is genetically predisposed. Chang rejects that conclusion and points to evidence of a genetic predisposition produced by several genes. We have a clear yes from Wirth and a clear no from Chang on what the research supports.
- E
A search can fail whether it was thorough or careless. Neither speaker evaluates how thoroughly the researchers searched. Chang questions the inference Wirth draws from their findings, not the amount of work they did.
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