The Quantitative Genetics of Phenotypic Error or Uniformity

The ε term is referred to by numerous synonyms in the literature like stochastic noise, biological variance, and error but is more commonly discussed as the inverse (ε−1) using words like uniformity, canalization, robustness, or stability depending upon the research field. In evolutionary theory, canalization is utilized to refer to the idea that selection functions to minimize the error (maximize the robustness) of a phenotype and that there should be genes controlling this phenomena (Waddington, 1942; Schmalhausen, 1949). Agricultural studies frequently focus upon uniformity wherein the goal is to decrease ε/increase uniformity to allow for increased planting densities and use of mechanization in crop production (Fasoula and Fasoula, 2002; Fasoula and Tollenaar, 2005). In most modern systems biology, genomics, and molecular biological studies, ε is implicitly or explicitly considered to be random variance when there is actually a significant genetic component (Barkai and Leibler, 1997; Albert et al., 2000; Albert and Barabasi, 2002; Kitano, 2004, 2007; Austin et al., 2006). The genetic component controls ε/uniformity by changing the connection of genes within a network through natural or induced mutation. These changed connections then increase or decrease the uniformity of the resulting phenotype. Thus, phenotypic noise shows a similar equation as the phenotype itself with a dependence upon genotype, environment and the resulting interaction