Baseparity
From Biomatics.org
Baseparity means that the ratios of A, T, G and C of a single strand DNA sequence are 1:1 and 1:1.
Baseparity is found all across the species.
Viroids are small but clear symmetries. Any prokaryotic and eukaryotic genomes shows some kind of baseparity with hundreds of nucleotides and longer.
Gene regions that code proteins tend to show disturbances in the baseparity.

History of baseparity research