KHAEMENES ACADEMY · BIOLOGY 10 · WEEK 22 · DAY 03

Gene–Environment Interaction & Reaction Norms

Model how the effect of genotype can depend on environmental conditions.

Safety, privacy and evidence boundary

Use fictional organisms and de-identified/public datasets. Do not infer intelligence, personality, worth, disease, ancestry, race, or family traits from genetics. Complex-trait models are population-level scientific tools, not labels for individuals.

Explicit science instruction

A gene–environment interaction occurs when genotypes respond differently across environments. A reaction norm plots phenotype against environment for different genotypes. Parallel lines suggest similar environmental response; nonparallel lines are consistent with interaction.

Correlation between genotype and environment can also complicate interpretation, so controlled designs or careful observational methods matter.

Worked example with reasoning

Fictional genotypes G1 and G2 grow 10 and 12 cm under low nutrient, but 20 and 15 cm under high nutrient. The genotype ranking reverses across environments, producing crossing reaction norms—strong evidence that genotype effect depends on environment in this model.

Guided question

Why is “gene versus environment” often the wrong question?

Independent work

  1. Plot two genotypes across three environments.
  2. Identify main genotype effect, environmental effect, and interaction pattern.
  3. Write one causal claim the data support and one they do not.
  4. State one confounder in an observational human study.

Misconception check

Environmental influence does not imply a trait is freely changeable, and genetic influence does not imply inevitability.

Formative understanding check

What visual pattern suggests interaction in a reaction-norm graph?

Worked response

Nonparallel genotype response lines, especially when differences change magnitude or direction across environments.

Open-book formative practice only; not an official mastery attempt or grade.

Mentor evidence conference

Ask Archaemenes to challenge the model, quantitative reasoning, and limits without inferring personal genetic or medical information.

Open Archaemenes

Teacher guidance

Foundation: use a pre-labeled reaction-norm graph. Core: interpret interaction without deterministic language. Extended: distinguish interaction from genotype–environment correlation and propose a stronger design.

Preserve learning evidence

Keep the model, data interpretation, correction note, and limitation in the matching Week 22 evidence field.