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** Index**

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4 Consequences for Variation and Covariation

In this section we will work through the matrix algebra to derive
expected variance and covariance components for a simplified model of
sibling interaction. We then show how this model can be adapted to
handle the specific cases of additive and dominant genetic, and shared
and non-shared environmental effects. Numerical examples of strong
competition and cooperation will be used to illustrate their effects
on the variances and covariances of twins and unrelated individuals
reared in the same home.

**Subsections**

Jeff Lessem
2002-03-21