Estimating the extent of parameter bias in the classical twin design: A comparison of parameter estimates from extended twin-family and classical twin designs
Estimating the extent of parameter bias in the classical twin design: A comparison of parameter estimates from extended twin-family and classical twin designs
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DOI：
10.1375/twin.8.3.214
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发表时间：
2005-06-01
影响因子：
0.9
通讯作者：
Keller, MC
中科院分区：
文献类型：
--
作者：
Coventry, WL;Keller, MC
经典的双胞胎设计(CTD)通过假设(1)可忽略的高阶上位性；(2)非加性遗传或共同环境效应不存在，从而产生两个潜在的偏倚来源，从而规避了参数不确定性(Eaves等人，1978；Grayson，1989)。由于扩展双家系设计(ETFD)使用了更多的唯一协方差观测值来估计参数，因此可以同时估计常见的环境遗传参数和非加性遗传参数。因此，ETFD修正了CTD参数估计中可能是最大的两个偏差来源(Keller&Coventry，2005)。在目前的论文中，我们通过比较所有已发表的ETFD参数估计和从相同数据得出的CTD参数估计来评估CTD中这种偏差的程度和其他潜在的偏差来源。对于某些表型，对共同环境的CTD估计低于对共同环境的ETFD估计，但对于其他表型(例如，雌性的身高和某些社会态度)，在ETFD中，看起来像是共同环境的东西被解析为分类交配。平均而言，非加性遗传因素的CTD估计比ETFD估计低43%，而加性遗传因素的CTD估计高63%。然而，CTD的广义遗传力估计仅比ETFD估计高18%，这突显出CTD对于估计广义遗传力是有用的，而不是狭义遗传力。这些结果表明，从字面上解释时，CTD估计可能具有误导性，但当正确解释时，尽管粗略，但很有用。
The classical twin design (CTD) circumvents parameter indeterminacy by assuming (1) negligible higher-order epistasis; and (2) either nonadditive genetic or common environmental effects are nonexistent, creating two potential sources of bias (Eaves et al., 1978; Grayson, 1989). Because the extended twin-family design (ETFD) uses many more unique covariance observations to estimate parameters, common environmental and nonadditive genetic parameters can be simultaneously estimated. The ETFD thereby corrects for what is likely to be the largest of the two sources of bias in CTD parameter estimates (Keller & Coventry, 2005). In the current paper, we assess the extent of this and other potential sources of bias in the CTD by comparing all published ETFD parameter estimates to CTD parameter estimates derived from the same data. CTD estimates of the common environment were lower than ETFD estimates of the common environment for some phenotypes, but for other phenotypes (e.g., stature in females and certain social attitudes), what appeared as the common environment was resolved to be assortative mating in the ETFD. On average, CTD estimates of nonadditive genetic factors were 43% lower, and additive genetic factors 63% higher, than ETFD estimates. However, broad-sense heritability estimates from the CTD were only 18% higher than ETFD estimates, highlighting that the CTD is useful for estimating broad-sense but not narrow-sense heritability. These results suggest that CTD estimates can be misleading when interpreted literally, but useful, albeit coarse, when interpreted properly.