SAT Reading & Writing · Command of Evidence (textual)
A genetic variant called CCR5-Δ32, which provides resistance to some strains of HIV, is relatively common in parts of Europe. A popular…
A genetic variant called CCR5-Δ32, which provides resistance to some strains of HIV, is relatively common in parts of Europe. A popular science article claims that the variant's frequency today proves it was strongly favored by natural selection during medieval outbreaks of plague. Which finding would most directly undermine the article's claim?
Answer and explanation
Answer: B: The historical claim linking the variant's frequency to plague selection remains actively debated among researchers, and the variant's current distribution does not require that explanation to be…
The article treats a specific historical explanation as proven fact, and B directly challenges that by noting the claim remains genuinely contested and isn't necessary to explain the variant's current distribution. A and C are background facts about the variant's function and distribution that don't address the plague-selection claim specifically. D is true but doesn't by itself address whether plague, instead of some other historical factor, explains the variant's frequency.
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