Figure 1.

Test System. a) Gene network [42] used as test system for illustrating the proposed methods. Solid arrows represent material flow, while dashed arrows indicate regulatory signals that either activate (+) or inhibit (-) a process. The network contains two genes, Gene 1 and 2. X₁ is the mRNA produced from gene 1, X₂ is the enzyme for which the gene codes, and X₃ is an inducer protein catalyzed by X₂. X₄ is the mRNA produced from Gene 2 and X₅ is a regulator protein for which the gene codes. Positive feedback from X₃ and negative feedback from X₅ are assumed in the production of mRNAs from the two genes. b) S-system model of the gene network, according to Hlavacek and Savageau [42] and Kikuchi et al. [21].