Do DNA viruses exist?
DNA viruses are ubiquitous worldwide, especially in marine environments where they form an important part of marine ecosystems, and infect both prokaryotes and eukaryotes.
Why do viruses have a small genome?
Small genome size is perfectly suited to virus replication, in which each infected host cell produces many copies of the viral genes from a single template. Such exponential replication places a premium on small genome size: the smaller the genome, the faster it can replicate.
Although viruses are generally the smallest genomes, as a collection of biological genomes they exhibit the greatest variation. The major difference is that some of the genomes are DNA whereas others are RNA. In addition, both DNA and RNA genomes can be either double- or single-stranded (ds or ss).
Do viruses have capsids?
Each virus possesses a protein capsid to protect its nucleic acid genome from the harsh environment. Virus capsids predominantly come in two shapes: helical and icosahedral.
With respect to the genome, viruses are broadly divided into DNA viruses and RNA viruses. Both DNA and RNA viruses can either single stranded or double stranded, with a circular, linear or segmented arrangement. DNA and RNA viruses are distinguished by their features, such as monopartite or multipartite.