Genome-wide association studies (GWAS) have identified thousands of genetic variants linked to complex traits like height and disease risk. However, each individual variant typically explains less than 1% of the variation. This 'missing heritability' puzzle—where identified genes explain far less than twin studies suggest should be heritable—remains an active area of research.
Based on the passage, it can be inferred that
genetic research has identified all factors contributing to complex traits
twin studies are less reliable than GWAS
our understanding of genetic contributions to complex traits may still be incomplete
each genetic variant has an enormous effect on complex traits
Correct Answer: C
Choice C is the best answer. The gap between expected and identified heritability is an unsolved puzzle.
- Context clues: Twin studies suggest more heritability than GWAS explains—"missing heritability."
- Meaning: Something genetic remains unaccounted for in current findings.
- Verify: It "remains an active area of research" precisely because understanding is incomplete.
💡 Strategy: When there's a gap between prediction and finding called a "puzzle," infer incomplete understanding.
Choice A is incorrect because there's a "missing heritability" gap. Choice B is incorrect because the passage doesn't say which is more reliable—they give different information. Choice D is incorrect because each variant explains "less than 1%"—small effects.