Explain gene-environment interaction with an example.

Explain gene-environment interaction with an example.

• A. The effect of a genetic predisposition depends on the environment; e.g., 5-HTT gene variants and stress increasing depression risk
• B. The effect of a gene is fixed regardless of environment
• C. Gene expression is unaffected by stress
• D. 5-HTT gene variants cause depression regardless of environment

Answer: (A)

Gene–environment interaction means that a genetic predisposition does not determine an outcome on its own—the environment can change how strongly that gene influences behavior or risk. A classic example looks at the serotonin transporter gene (5-HTT) and stressful life events. People with one or two short variants of this gene show a greater increase in depression risk after experiencing stress compared with those who have two long variants. This shows the same genetic factor can lead to different outcomes depending on the environmental context, and it isn’t simply that the gene causes depression regardless of anything else. It’s also not a fixed effect—environmental factors like stress can amplify or buffer genetic influences, and stress can even affect how genes are expressed. So this interaction is about how genes and environment work together to shape risk, rather than acting in isolation.

Gene–environment interaction means that a genetic predisposition does not determine an outcome on its own—the environment can change how strongly that gene influences behavior or risk. A classic example looks at the serotonin transporter gene (5-HTT) and stressful life events. People with one or two short variants of this gene show a greater increase in depression risk after experiencing stress compared with those who have two long variants. This shows the same genetic factor can lead to different outcomes depending on the environmental context, and it isn’t simply that the gene causes depression regardless of anything else. It’s also not a fixed effect—environmental factors like stress can amplify or buffer genetic influences, and stress can even affect how genes are expressed. So this interaction is about how genes and environment work together to shape risk, rather than acting in isolation.