Behavioral Genetics and Gene–Environment Interaction (7A) Practice Test

A study examined gene–environment correlation in sports participation. Adolescents were genotyped for a variant associated with higher endurance capacity. The school offered multiple sports with open tryouts and no fees. Researchers found that students with the endurance-associated genotype were more likely to join cross-country or soccer rather than non-endurance clubs, and they reported enjoying long-duration exercise more. Participation predicted improved cardiovascular fitness at follow-up. The authors noted that genetic differences may have influenced selection into certain activities, increasing exposure to training environments.

What prediction is most consistent with gene-environment correlation as described?

Researchers conducted a twin study on language development in bilingual homes. Monozygotic (MZ) and dizygotic (DZ) twins were assessed at age 5 on vocabulary in the community language. Some families used a bilingual environment at home (regular use of two languages), while others used only the community language. In monolingual homes, MZ twins were more similar than DZ twins in vocabulary. In bilingual homes, average vocabulary in the community language was slightly lower, and MZ–DZ differences in similarity were smaller. The authors suggested the language environment altered the extent to which genetic differences explained variability in vocabulary.

Based on the vignette, which conclusion about genetic predisposition and environment is supported?