Fig. 2. Environmental effects on the genotype can be of genetic origin. If environment affects the level and consequent binding of a transcription factor (TF) to the gene regulatory sequence (GRS), for example, then different phenotypes are observed depending on the environmentally induced differences in the induction of the gene. If the structure of the gene regulatory sequence changes, binding of the transcription factor can be affected, leading to changes in gene expression and consequent changes in the phenotype.