Keightley P D, Kacser H
Department of Genetics, University of Edinburgh, Scotland.
Genetics. 1987 Oct;117(2):319-29. doi: 10.1093/genetics/117.2.319.
It is a common observation that most mutants have similar dominance relations for all the characters they are known to affect. As a model of pleiotropic effects we investigate a branched pathway where the two outputs represent two characters whose variation is affected by changes in any of the genetically specified enzymes in the system. We consider the effects on the phenotype (fluxes or intermediate metabolites) of substitutions at one locus represented by enzyme activities of the two homozygotes (mutant and wild type) and that of the heterozygote. Dominance indices for the characters pleiotropically connected by the metabolic system are calculated. We show that if enzymes behave 'linearly,' (first order), that is if saturation and feedback inhibition or other nonlinearities are absent, all fluxes and pools have identical dominance relations. The presence of such nonlinearity, however, leads to differences in dominance between different characters and we define the conditions where such differences can be important.
一个常见的观察结果是，大多数突变体对它们已知影响的所有性状都具有相似的显性关系。作为多效性效应的一个模型，我们研究了一个分支途径，其中两个输出代表两个性状，它们的变异受到系统中任何遗传指定酶的变化的影响。我们考虑了由两个纯合子（突变体和野生型）以及杂合子的酶活性所代表的一个位点上的替代对表型（通量或中间代谢物）的影响。计算了由代谢系统多效性连接的性状的显性指数。我们表明，如果酶表现为“线性”（一级），即如果不存在饱和、反馈抑制或其他非线性，所有通量和库都具有相同的显性关系。然而，这种非线性的存在会导致不同性状之间的显性差异，并且我们定义了这种差异可能很重要的条件。
