Autocatalysis indirect

Finally, DNA/RNA must not be viewed in isolation for they have to be synthesised indirectly by autocatalysis and their expression as proteins is complicated. 

An alternative form of positive feedback is indirect autocatalysis. Here, although / and Jjj are both negative, the combined effects of species i on species j and of j on i are such that a rise in one of these concentrations ultimately leads to an increase in how rapidly it is produced. Mathematically, we require that JyJji > 0. There are two possibilities competition, in which i inhibits y, and j inhibits i, so that both Jacobian elements are negative and symbiosis, in which the two species activate each other, resulting in positive Jy and /y,. A simple example of symbiosis arises from introducing an intermediate Y and breaking down reaction (5.19) into a pair of steps ... 

Luo and Epstein (1990) identified three types of negative feedback. The most common one in chemical oscillators is referred to as coproduct autocontrol. In this type of negative feedback, the positive feedback step, generally autocatalysis, generates not only more of the autocatalyst, but also a second product, or coproduct. This latter species reacts, either directly or indirectly, in such a way as to remove the autocatalyst and ultimately to shut down the autocatalysis. This pattern can be seen in the Oregonator (Field and Noyes, 1974b) ... 

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