Various gene regulatory networks under consideration.

<p><b>(A)</b> Positive feedback with additional negative feedback motif, where X (total protein) activates the synthesis of another protein Y_P which negatively regulates X population level. <b>(B)</b> Double positive feedback motifs, where X (total protein) activates the synthesis of another protein Y_P which positively regulates the synthesis of X. In all the cases X autoregulates its own synthesis positively. Here M_P denotes mRNA of P, Y_P denotes another protein and Y_M is the mRNA of protein Y_P. Detailed mechanistic models are given in (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0136668#pone.0136668.s006" target="_blank">S6 Fig</a>).