The sequence data in the world-wide databases on codons and ribosome RNA (rRNA) shows that the average density ratio of purine and pyrimidine for many of species is around 1.3, while the average density ratio in transfer RNA (tRNA) is around 1.1. The reason for this difference between tRNA, codons, and rRNA is clarified in the present report. Finally, we show that these asymmetries in density promote repeat arrays and inverse repeats inside RNA and DNA.
Key words Density ratio of bases - tRNA - rRNA - Asymmetry - Repeat - RNAi
This work was presented, in part, at the 9th International Symposium on Artificial Life and Robotics, Oita, Japan, January 28–30, 2004