“…(II) A Two-Gene System with Cross-Regulation . The second model is a two-gene activation-inhibition system with cross-regulation (studied by Polynikis et al [ 15 ], Widder et al [ 17 ], Chen et al [ 32 ], You [ 26 ], and You et al [ 27 ]) where, for i = 1,2, r i is the concentration of mRNA R i produced by gene g i , p i is the concentration of protein P i , m i is the maximal transcription rate of gene g i , κ i is the translation rate of mRNA R i , and γ i and μ i are the degradation rates of mRNA R i and protein P i , respectively. The functions are the Hill functions of activation and repression, respectively.…”