A theoretical solution to the bootstrap problem of life that requires DNA to make protein and vice versa. The concept was first put forward by Manfred Eigen, drawing on the ideas of feedback loops proposed by Norbert Weiner (one of the origional cyberneticists, along with Claude Shannon and Von Neumann).

A simple example is that of two ribozymes that catalyse the formation of each other:

  A   B

This means that each RNA molecule is the gene for the other, and any change in one will affect the whole system in a non-linear way.