PrepTest 112, Section 4, Question 10
Twelve healthy volunteers with the Apo-A-IV-1 gene and(67 more words not shown)
Which one of the following(8 more words not shown)
- AApproximately half the(8 more words not shown)
- BMost of those(17 more words not shown)
- CThe bodies of(15 more words not shown)
- DThe presence of(16 more words not shown)
- EThe presence of(10 more words not shown)
Reading the argument
The two groups ate the same added high-cholesterol food. Why did blood cholesterol rise in one group and stay steady in the other?
The gene variants are the stated difference between the groups, so I'd consider whether that difference helps explain their responses. I'll call them variant 1 and variant 2 to keep the names manageable. The variant 1 group's blood cholesterol rose 20 percent; the variant 2 group's did not rise.
Keep the food and the blood measurements separate. Consuming cholesterol is one thing; seeing a higher measured level in the blood is another. The study suggests variant 2 may help prevent that rise, but it doesn't tell us exactly how. A steady level doesn't establish that no cholesterol ever entered the blood.
What we’re looking for
The question asks what is most strongly supported. My prediction is that variant 2 may inhibit the increase. We should keep that as a possibility supported by the contrast, rather than turn it into a proven mechanism or a recommendation about what most people should eat.
Working the answers
- A
Twelve people in each group means half this study's participants had each variant. It doesn't tell us how common either variant is in the population. Researchers could recruit equal groups even if one variant were rare. Also, variant 2 was associated with unchanged levels, not a reduction below the starting level. A adds both a population claim and a lowering effect.
- B
The study didn't test a low-cholesterol diet, and it doesn't tell us about most people at risk of heart disease. A particular response to added cholesterol doesn't establish what removing cholesterol would do across that broader group. B goes beyond the limited comparison the experiment supplies.
- C
This invents a mechanism and a trigger. The unchanged blood level doesn't tell us that the body excretes cholesterol, much less that excretion starts at a certain threshold. A steady level could result from several processes. We can consider a protective effect without knowing the process responsible for it.
- D
Variant 1 is the one associated with a rise in blood cholesterol, while the passage links high blood cholesterol with increased heart-disease risk. That gives us no reason to infer a lower risk from variant 1. We also lack the starting levels and direct heart-disease outcomes needed for a precise risk comparison. D isn't the supported direction of the result.
- ECorrect
The presence of Apo-A-IV-2 may inhibit the rise in blood cholesterol. The group with that variant maintained its level despite the added food, while the other group's level rose. That difference supports the proposed possibility.
The word 'may' fits the evidence. We aren't establishing that the variant is the only explanation, that it removes cholesterol in a particular way, or that its carriers cannot develop heart disease. E stays with the limited effect the study suggests.
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