Abstract

The classical twin design is used to decompose phenotypic variance into genetic and environmental variance components. In practice, for reasons of identification, either an ADE or an ACE twin model is fitted, i.e., models with three variance components. Jöreskog proposed to use the Moore-Penrose inverse to estimate the four genetic and environmental variance components in the ACDE twin model. We demonstrate that the variance components thus obtained do not equal the true genetic and environmental variance components. Given a ACDE model, resorting to an ADE or ACE model or applying Jöreskog’s method will not produce correct results. However, it is possible that Jöreskog’s method will produce a better approximation to the true variance components under certain configurations of A, D, C, and E variance components.

摘要

经典双胞胎设计用于将表型变异分解为遗传和环境变异成分。实际上，出于识别的原因，拟合了 ADE 或 ACE 双模型，即具有三个方差分量的模型。Jöreskog 提议使用 Moore-Penrose 逆来估计 ACDE 双模型中的四个遗传和环境方差分量。我们证明由此获得的方差分量不等于真正的遗传和环境方差分量。给定一个 ACDE 模型，求助于 ADE 或 ACE 模型或应用 Jöreskog 的方法不会产生正确的结果。但是，在 A、D、C 和 E 方差分量的某些配置下，Jöreskog 的方法可能会更好地逼近真实方差分量。