Nucleic acids are biological molecules essential for life. Together with proteins, nucleic acids make up the most important macromolecules; each is found in abundance in all living things, where they function in encoding, transmitting and expressing genetic information.
Single strand Nucleic Acids are called RNA (RiboNucleic Acid). All Viruses are made up of RNA
Double strand (Double Helix) Nucleic Acids are called DNA (DeoxyriboNucleic Acid). Most Cells have of DNA in their nucleus.
Tripple strand (Tripple Helix) Nucleic Acids (TNA?) are being researched in laboratories. Certain mutants(or Aliens) have been reported to have TNA? in their nucleus.
Acording to some theorists, we humans will evolve to have Tripple Helix in our Cell's Nucleus; that is, our next stage of evolution could be Tripple Strand Nucleic Acids. The timeframe given for this change is between Oct 28 2011, and Dec 21, 2012.