Fig. 6

A scheme describing the routes concerning replication and transcription in the system. The chromosome is in a circular form: thick lines represent the sense chain, while thin lines represent the antisense chain. RNA is drawn in black, while DNA in red. Broad white arrows highlight the way in which the ribozymes (crescent-shapes) are created: the linear sense RNA, which arises from the spontaneous break of the sense chain of the RNA chromosome or partial copying of the antisense chain of the RNA or DNA chromosome, may be readily broken at sites (marked by short bands) between the linked genes (the so-called “self-cleaving” feature, see [15] for details). The routes which are led in the original pure RNA-based system can be easily identified at the left part, where no DNA (red line) is involved. When Nrr begins to take effect, “reverse transcription” may happen and give rise to the DNA chromosome (see the routes labeled by white triangles). When a thorough genetic takeover is completed, DNA’s replication (labeled by stars) and its transcription to the sense RNA chain (labeled by black triangles) would constitute the most significant information flow in the living system