The genomic content of viruses can be made of RNA or DNA and can be single-stranded or double-stranded.
All viruses have genetic material made of nucleic acids. You, like all other cell-based life, use DNA as your genetic material. Viruses, on the other hand, may use either RNA or DNA, both of which are types of nucleic acid. Two differences distinguish DNA from RNA: RNA contains the sugar ribose. In contrast, DNA contains the sugar deoxyribose – hence DNA and RNA and RNA has the nucleic acid uracil while DNA contains Thymine.
We often think of DNA as double-stranded and RNA as single-stranded, since that’s typically the case in our cells. However, viruses can have all possible combos of strandedness and nucleic acid type (double-stranded DNA, double-stranded RNA, single-stranded DNA, or single-stranded RNA). Viral genomes also come in various shapes, sizes, and varieties, though they are generally much smaller than the genomes of cellular organisms.
Notably, DNA and RNA viruses always use the same genetic code as eukaryotic and prokaryotic cells. This similarity allows them to infect host cells and use the genetic material and proteins in the host cell to produce copies to reproduce. If they didn’t have similar genetic material, they would have no way to reprogram their host cells!
Key Points
• The genomic content of viruses can be made of RNA or DNA and can be single-stranded or double-stranded.
• Two differences distinguish DNA from RNA: RNA contains the sugar ribose, while DNA contains the sugar deoxyribose and RNA has the nucleic acid uracil while DNA contains Thymine.
Key Terms
capsid: protein shell of a virus that contains the genetic material
envelope: an external lipid membrane surrounding the capsid that some viruses have
nucleic acids: are macromolecules that store genetic information and enable protein production, these commonly include DNA and RNA
DNA: deoxyribonucleic acid is a double helix carrying genetic instructions
RNA: a ribonucleic acid is a single-stranded form of genetic information where the bases are the same as DNA except for Thymine which is replaced with Uracil
eukaryotic: contain a nucleus that is enclosed by a plasma membrane
prokaryotes: organisms whose cells do not contain a distinct nucleus, bounded by a nuclear envelope
ribose: a simple sugar and carbohydrate with the molecular formula C5H10O5
deoxyribose: a sugar derived from ribose by replacing a hydroxyl group with hydrogen.
