Crop Science Department, University of Saskatchewan, Saskatoon, Canada.
Theor Appl Genet. 1972 Jan;42(3):119-24. doi: 10.1007/BF00583413.
The phenotypes associated with the nine genotypes in a quantitative genetic system consisting of two loci, each having two alleles can be described in terms of nine parameters, giving a system of nine linear equations. Populations with desired magnitudes and known nature of intra- and interlocus interactions are obtained by the use of this linear combination model. The total sums of squares for genotypes in these populations are partitioned into orthogonal components denoting additive and dominance effects of the two loci and the four types of nonallelic interactions between them. In most cases, the relative magnitudes of dominance and epistatic variances are found to be considerably smaller than the actual proportions of these genetic effects. Duplicate interaction produces larger epistatic variance than complementary type of gene interaction. At the higher levels of epistasis, dominant epistasis yields much larger epistatic variance than recessive epistasis. No epistatic variance is produced in the absence of epistatic effects. But, appreciable contributions of additive and dominance gene actions to the total genotypic variability are obtained even in the complete absence of these effects, if additive × dominance and dominance × dominance epistatic effects, respectively, are present. It is concluded that in elucidating the nature of gene action in simplified genetic systems, the estimates of first degree parameters obtained from the linear combination model are more useful than the orthogonal components of genotypic sum of squares.
在一个由两个位点组成的数量遗传系统中，每个位点有两个等位基因，与九个基因型相关的表型可以用九个参数来描述，从而形成一个由九个线性方程组成的系统。通过使用这种线性组合模型，可以获得具有所需幅度和已知等位基因内和等位基因间相互作用性质的群体。这些群体中基因型的总平方和被分成正交分量，表示两个位点的加性和显性效应以及它们之间四种类型的非等位基因相互作用。在大多数情况下，发现显性和上位方差的相对大小明显小于这些遗传效应的实际比例。重复的相互作用产生的上位方差比互补类型的基因相互作用更大。在较高的上位水平上，显性上位作用产生的上位方差比隐性上位作用大得多。如果不存在上位效应，则不会产生上位方差。但是，即使完全不存在这些效应，如果分别存在加性×显性上位效应和显性×显性上位效应，那么对总基因型变异性的加性和显性基因作用的贡献仍然相当大。因此，可以得出结论，在阐明简化遗传系统中的基因作用性质时，从线性组合模型获得的一阶参数估计比基因型总和的正交分量更有用。
