During high school you might have learned two very basic rules about nucleic acid: DNA and RNA. Deoxyribonucleic acid (DNA) is a double stranded molecule, i.e. it consists of two strand of DNA bound together and RNA is a single stranded molecule.
But this rule may not hold true in case of viruses. Viruses are only creatures that have genetic material composed of single stranded DNA / double stranded RNA.
- Viruses having double stranded RNA as their genome: virus of family Reoviridae (Rotavirus, Colorado tick fever virus) and Birnaviridae have double stranded RNA as their genome.
- Virus having single stranded DNA as their genome: virus of family Parvoviridae (Parvovirus B-19) possesses single stranded DNA.
Other unique properties of viral genomes
- Viral genomes are either DNA or RNA but not both
- Nucleic acid can be either linear or circular
- RNA can exist in several pieces. Influenza virus and rotavirus have segmented RNA genome
- Almost all viruses are haploid, i.e. they contains single copy of genome with a major exception of retrovirus family which is diploid (have two copies of their RNA genome).