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

A twin study examined how neighborhood context moderates genetic influence on adolescent rule-breaking. Researchers recruited monozygotic (MZ) and dizygotic (DZ) twin pairs raised together. Neighborhoods were classified as high-monitoring (e.g., strong informal social control, adults intervene) or low-monitoring. Rule-breaking was assessed via confidential self-report. In low-monitoring neighborhoods, MZ twins were much more similar to each other in rule-breaking than DZ twins. In high-monitoring neighborhoods, MZ and DZ similarity was more comparable, and overall rule-breaking was lower. The authors interpreted this as evidence that environmental constraints can reduce the extent to which genetic differences translate into behavioral differences. Which finding is most consistent with the passage’s discussion on gene–environment interaction?

Researchers studied gene–environment interaction in adolescent sleep and attention. Participants were genotyped for a common variant in a dopamine-related gene (alleles X and x) previously linked to higher distractibility, but only under certain conditions. For 6 weeks, students attended either an early-start school (first class at 7:20 a.m.) or a later-start school (first class at 8:50 a.m.). Both schools had similar class sizes and curricula. Attention was measured weekly using the same computerized task. In the early-start environment, students with genotype XX showed a larger decline in attention scores over time than students with Xx or xx. In the later-start environment, attention scores were similar across genotypes, and overall declines were minimal. The investigators concluded that the school schedule moderated the association between genotype and attention.

Which finding is most consistent with the vignette’s discussion on gene–environment interaction?