DNA viruses like poxviruses, herpesviruses, and hepatitis B viruses use DNA as their genetic material. Herpesviruses have larger virions and genomes than adenoviruses. They enter cells through fusion with the plasma membrane or endocytosis. During replication, herpesviruses use host enzymes to transcribe early genes that regulate expression of late genes for structural proteins. Virions assemble in the nucleus and acquire an envelope as they bud through the inner nuclear membrane. Viral genomes evolve through spontaneous or induced mutation during replication and by recombining genetic material within or between viruses through breaking and rejoining DNA or RNA.

1. DNA VIRUSES-Dnavirus is a virus that has DNA (deoxyribonucleic acid) as its genetic material. -They are usually Large, Icosahedral, enveloped in Lipoproteins-Do not have polymerase enzymes, and cause Latent infection-Examples include Poxviruses, Herpesviruses, hepadnaviruses, Hepatitis b.

2. HERPESVIRUSES -Larger virions than adenoviruses(180 - 200nm)-Larger genome (three to five times) than adenoviruses. -Linear, double-stranded DNA, Enveloped, icosahedral virus (this means that lipid solvents readily inactivate these viruses)

4. Adsorption and penetration-Many herpesviruses, including herpes simplex virus, can fuse directly with the plasma membrane (results in partial uncoating). -Such fusion with the plasma membrane has implications for both the virus and the host cell.

5. Earlyphase-Early transcription (the mRNAs made during this phase are the alpha and beta mRNAs). -Herpes viruses use host RNA polymerase-The virus uses host mRNA modification enzymes.-Initially, alpha-mRNAs are transcribed-Beta-mRNAs are transcribed by the host RNA polymerase again-Beta proteins are involved in gene expression regulation-They decrease alpha-gene expression and are needed for gamma gene expression.

6. Late phase-Herpesvirusescode for several proteins, in addition to the DNA polymerase, that are needed for DNA replication. -DNA replication is accompanied by a lot of recombination-The replicated DNA is present as long concatamericmolecules-These are cleaved to genome-size lengths when DNA is packaged into the virion.

7. Late transcription: -Late transcription occurs after DNA replication. -Gamma mRNAs are made and are translated in the cytoplasm. -Gamma proteins are predominantly structural. -There is decreased expression of beta genes in the late stage. -In herpes viruses there is no apparent organization of the genome into blocks for either early or late transcription.

8. Assembly-Assembly occurs in the nucleus. -A capsid is formed and the DNA enters the capsid. -The capsids acquire an envelope by budding through areas of the inner nuclear membrane which have viral membrane proteins inserted into them. -The virus envelope then fuses with the outer nuclear membrane and the de-enveloped nucleocapisid is delivered into the cytoplasm -It then becomes re-enveloped by budding into Golgi-derived vesicles and is then released.-The late protein required for transcription of immediate early mRNAs in the next round of infection is packaged in the virion.

9. Evolution of Viruses:Viral genomes undergo genetic change by mutation, either spontaneous or induced mutation, and by recombination.

10. Recombination may be either intramolecular or, among viruses with divided genomes, by reassortment.1.Mutations:These arise naturally during viral replication2. Exchange of Genetic material:This involves breaking of covalent bonds within the nucleic acid, exchange of genetic information, and reforming of covalent bonds. This kind of break/join recombination is common in DNA viruses or those RNA viruses which have a DNA phase (retroviruses). The host cell has recombination systems for DNA. If a virus has a segmented genome and if two variants of that virus infect a single cell, progeny virions can result with some segments from one parent, some from the other.