Introduction to Evolutionary Genomics by Naruya Saitou

Author:Naruya Saitou
Language: eng
Format: epub, pdf
ISBN: 9783319926421
Publisher: Springer International Publishing

10.3 DNA Viruses

Most of bacterial and archaeal viruses (phages) are DNA viruses , and genome sizes of DNA viruses are often in order of 104 and are much larger than those of RNA viruses [3]. Group D1 (Baltimore class II) viruses have single-stranded (+) circular DNA genomes, and examples are φX174 bacteriophage and M13 bacteriophage. It may be noted that the genome sequence of φX174 bacteriophage was determined by Frederick Sanger’s group in 1977 [7]. Group D2 (Baltimore class II) viruses have single-stranded (+) linear DNA genomes, and an example is Parvovirus. Group D3 (Baltimore class I) viruses have double-stranded circular DNA genomes, and examples are SV40 and Polyomavirus. Group D4 (Baltimore class I) viruses have double-stranded linear DNA genomes, and examples are T4 phage, Vaccinia virus, and herpes virus. Group D5 (Baltimore class I) viruses have double-stranded linear (and proteins are attached at both ends) DNA genomes, and an example is Adenovirus. Group D6 (Baltimore class I) viruses have double-stranded linear (but and both ends are closed) DNA genomes, and an example is Poxvirus. Finally, Group D7 (Baltimore class VII) viruses have double-stranded linear DNA genomes, with RNA intermediate in life cycle. An example is Hepatitis B virus.

Some DNA genome viruses are unusually large and similar to a small bacterial genome. The virus with the largest genome size so far found is Pandoravirus salinus parasitic to a protist ameba. This giant virus has 2.47 Mb genome size, and there are 2556 Protein-coding genes [8].

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