5.14 The Effects of Environment and Behavior on Genetic Expression

Genes Aren't Destiny

Epigenetics is the study of how environment and behavior influence gene expression without altering the underlying DNA sequence. Factors like stress, diet, toxins, and social experiences can turn genes 'on' or 'off,' affecting physical and mental health outcomes. This explains why identical twins with the same genotype can develop differently over time.

Gene-Environment Interaction

Gene-environment interaction means genetic predispositions can be expressed differently depending on environmental context. A person may carry a genetic risk for a disorder (like depression) but only develop it if exposed to certain environmental triggers (like chronic stress or trauma), showing genes set potential, not certainty.

Behavior Shapes Biology

Lifestyle choices—exercise, diet, substance use, and stress management—can directly influence gene expression and even be passed to offspring through epigenetic markers. This reciprocal relationship shows psychology's biopsychosocial approach: biology influences behavior, but behavior and environment also influence biology.

Key terms

Epigenetics

Study of how environment and behavior influence gene expression without changing the DNA sequence.

Gene-environment interaction

The idea that genetic predispositions may only be expressed under certain environmental conditions.

Why identical twins can differ

Despite sharing DNA, differing environments and experiences can cause different genes to be expressed, leading to different traits or health outcomes.

Example of epigenetic trigger

Chronic stress or trauma can activate genetic risk for depression in someone predisposed to it.

Biopsychosocial link to epigenetics

Shows biology (genes) and environment/behavior interact reciprocally to shape psychological and physical health.

Try an AP-style question

What does this demonstrate?

1. Classical conditioning
2. Genetic mutation
3. Heritability of licking
4. Epigenetic effects of experience