Horizontal gene transfer occurs when an organism of one species acquires genetic material from an organism of another species through...
GMAT Craft and Structure : (Structure) Questions
Horizontal gene transfer occurs when an organism of one species acquires genetic material from an organism of another species through nonreproductive means. The genetic material can then be transferred 'vertically' in the second species—that is, through reproductive inheritance. Scientist Atma Ivancevic and her team have hypothesized infection by invertebrate parasites as a mechanism of horizontal gene transfer between vertebrate species: while feeding, a parasite could acquire a gene from one host, then relocate to a host from a different vertebrate species and transfer the gene to it in turn.
Which choice best describes the function of the underlined portion in the text as a whole?
It explains why parasites are less susceptible to horizontal gene transfer than their hosts are.
It clarifies why some genes are more likely to be transferred horizontally than others are.
It contrasts how horizontal gene transfer occurs among vertebrates with how it occurs among invertebrates.
It describes a means by which horizontal gene transfer might occur among vertebrates.
Step 1: Decode and Map the Passage
Passage Analysis Table
| Text from Passage | Analysis |
|---|---|
| "Horizontal gene transfer occurs when an organism of one species acquires genetic material from an organism of another species through nonreproductive means." |
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| "The genetic material can then be transferred 'vertically' in the second species—that is, through reproductive inheritance." |
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| "Scientist Atma Ivancevic and her team have hypothesized infection by invertebrate parasites as a mechanism of horizontal gene transfer between vertebrate species:" |
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| "while feeding, a parasite could acquire a gene from one host, then relocate to a host from a different vertebrate species and transfer the gene to it in turn." |
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Passage Architecture & Core Elements
Main Point: Scientists hypothesize that parasites could facilitate horizontal gene transfer between vertebrate species by acquiring genes from one host and transferring them to another.
Argument Flow: The passage begins by defining horizontal gene transfer, clarifies how it continues through normal reproduction, then presents Ivancevic's specific hypothesis about how parasites could serve as the vehicle for this transfer, ending with a detailed explanation of the proposed mechanism.
Step 2: Interpret the Question Precisely
What's being asked? The function of the underlined portion within the overall text
What type of answer do we need? How this specific section serves the passage's purpose
Any limiting keywords? "underlined portion" limits our focus to that specific sentence, and "in the text as a whole" means we need to consider its role in the broader context
Step 3: Prethink the Answer
- Looking at our analysis, the underlined portion takes Ivancevic's general hypothesis about parasites and breaks it down into specific steps
- It's essentially the "how" that follows the "what"—explaining the actual mechanism by which parasites could facilitate horizontal gene transfer between vertebrates
- The right answer should recognize that this portion provides the detailed process or mechanism for how the hypothesis would work in practice
- It's not comparing different methods or explaining why some approaches work better than others—it's simply describing one possible way horizontal gene transfer could occur
- So the right answer should describe this portion as explaining a mechanism or process for horizontal gene transfer among vertebrates
It explains why parasites are less susceptible to horizontal gene transfer than their hosts are.
- Claims the text explains parasite susceptibility to gene transfer
- The passage doesn't discuss how susceptible parasites are—it focuses on how they could facilitate transfer between other organisms
- Misreads the parasites' role as carriers rather than recipients
It clarifies why some genes are more likely to be transferred horizontally than others are.
- Suggests the text explains gene selectivity in horizontal transfer
- The underlined portion doesn't address which genes transfer more easily
- Focuses on mechanism rather than gene characteristics
It contrasts how horizontal gene transfer occurs among vertebrates with how it occurs among invertebrates.
- Claims there's a contrast between vertebrate and invertebrate gene transfer methods
- No comparison is being made—the passage only discusses one proposed mechanism
- What trap this represents: Students might see "invertebrate parasites" and "vertebrate species" and assume a comparison is being drawn
It describes a means by which horizontal gene transfer might occur among vertebrates.
- Accurately identifies that the underlined portion describes a mechanism for horizontal gene transfer
- Correctly specifies this applies to vertebrates (the hosts in the example)
- Matches our prethinking about explaining the "how" of the hypothesis