Table 1.
Contributions of Genetic and Environmental Effects, and Various Types of Genotype × Environment Interaction Effects to Sibling Resemblance and to the Total Variance in a Population
| Average Genetic Sharing | Genetic Effects (G) | Shared Environment Effects (SE) | Nonshared Environment Effects (NSE) | Genetic × Shared Environment Effects (GxSE) | Genetic × Nonshared Environment Effects (GxNSE) | |
|---|---|---|---|---|---|---|
| Identical twins reared together | 100% | 1.0 | 1.0 | 0.0 | 1.0 × 1.0 = 1.0 | 1.0 × 0.0 = 0.0 |
| Fraternal twins and full sibling pairs reared together | 50% | 0.5 | 1.0 | 0.0 | 0.5 × 1.0 = 0.5 | 0.5 × 0.0 = 0.0 |
| Genetically unrelated siblings reared together | 0% | 0.0 | 1.0 | 0.0 | 0.0 × 1.0 = 0.0 | 0.0 × 0.0 = 0.0 |
| Identical twins reared apart | 100% | 1.0 | 0.0 | 0.0 | 1.0 × 0.0 = 0.0 | 1.0 × 0.0 = 0.0 |
| Fraternal twins and full sibling pairs reared apart | 50% | 0.5 | 0.0 | 0.0 | 0.5 × 0.0 = 0.0 | 0.5 × 0.0 = 0.0 |
| Total population variance | — | 1.0 | 1.0 | 1.0 | 1.0 × 1.0 = 1.0 | 1.0 × 1.0 = 1.0 |
NOTE: A coefficient of 1.0 indicates a high contribution, a coefficient of 0.5 an intermediate contribution, and a coefficient of 0 no contribution. SOURCE: Heath et al. 2002.