Transcriptional noise is known to be an important cause of cellular heterogeneity and
phenotypic variation. The extent to which molecular interaction networks may have evolved
to either filter or exploit transcriptional noise is a much debated question. The yeast genetic
network regulating galactose metabolism involves two proteins, Gal3p and Gal80p, that feed
back positively and negatively, respectively, on GAL gene expression. Using kinetic
modeling and experimental validation, we demonstrate that these feedback interactions …

In this section we briefly present our mathematical model of the yeast galactose utilization
pathway. This model is based on an earlier published model [1], with some simplifications.
The simulation results in this study were obtained using the chemical kinetics modeling
program Dizzy [2]. This software is available (under a free and open-source license) on the
World Wide Web at http://magnet. systemsbiology. net/software/Dizzy. The species names in
the model are defined in Table 1. In addition to the dynamical symbols defined in Table 1 …