Figure 2. Phenotypic impact of the genetic background.

A: An allele present in different genetic backgrounds results in the same phenotypic outcome at the organismal level. However, this does not mean that intermediate phenotypes such as molecular traits (e.g. gene expression level) will be the same. Every layer of intermediate phenotype acts as a lens that can deflect the phenotype in a specific way with the organism phenotype as the focal point of all these superimposed lenses. B: Some mutations, however, alter intermediate phenotypes and change the final organism phenotype.