5 - General rules on the replication of DNA viruses (s.s....

Info iconThis preview shows pages 1–8. Sign up to view the full content.

View Full Document Right Arrow Icon
General rules on the replication of DNA viruses (s.s. and d.s.) 1. Use DNA as template and synthesize the new strand in a 5' Æ 3' direction. 2. A primer with a free 3'-OH end (DNA or RNA or a protein) is required. 3. Replication of DNA begins and ends from specific sites in the template, termed origin and termini, respectively. 4. Each parent strand of a DNA duplex is copied to produce two identical daughter molecules.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Replication origin All except the smallest viral DNA molecules are replicated from two or three origins. In bidirectional replication, two replication forks are generated at a single origin. However, since DNA synthesis proceeds from 5' to 3', only the 'leading strand' can be synthesized continuously whereas the 'lagging strand' is synthesized by a discontinuous mechanism. The discontinuous mechanism will create a shorter end at the 5'end of the lagging strand. Viruses with linera DNA genomes have evloved a variety of elegant mechanisms to ensure complete replication of the whole genomes.
Background image of page 2
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 4
S.S. DNA viruses There are only two families of s.s. DNA viruses: Circoviridae and parvoviridae. Both virus families have (+) sense genome. Little is known about the Circoviridae. Parvoviridae Single stranded, linear, 5 kb. Non-enveloped, icosahedron, 20-26nm in diameter.
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Herpesviruses z Name comes from the Greek 'Herpein' - = chronic/latent/recurrent infections. z In 1950, Burnet and Buddingh showed that HSV could become latent after a primary infection and reactivate after later provocation. z Weller (1954) isolated VZV from chicken pox and zoster, verifying the same causal agent. z ~100 Herpesviruses have been isolated. z 8 known human Herpesviruses. z The family is divided into 3 Sub-families: Alphaherpesvirinae: Simplexvirus human herpesvirus 1, 2 (HSV-1, HSV-2) Varicellovirus human herpesvirus 3 (VZV) Betaherpesvirinae: Cytomegalovirus human herpesvirus 5 (CMV) Muromegalovirus mouse cytomegalovirus 1 Roseolovirus human herpesvirus 6, 7 ( HHV-6 , HHV-7 ) Gammaherpesvirinae: Lymphocryptovirus human herpesvirus 4 (EBV) Rhadinovirus human herpesvirus 8 (HHV-8) z Large genomes: up to 235kbp DNA z Complex viruses ~35 virion proteins. z All encode a variety of enzymes involved in nucleic acid metabolism, DNA synthesis and protein processing (protein kinase). z Similar in terms of virion structure and genome organization: Size: 180-200nm Envelope: Present; associated glycoproteins . Tegument: Protein-filled region between capsid and envelope. Capsid: Icosahedral, 95-105nm diameter; 162 hexagonal capsomers. Core: Toroidal (DNA around protein), ~75nm diameter. Genome: Linear, d/s DNA, 130-230kbp Replication: Nuclear. Assembly: Nuclear. Common Antigens: None!
Background image of page 6
Structure: z The core consists of a toroidal shape with the large DNA genome winds around a proteinaceous core. z
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 8
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 22

5 - General rules on the replication of DNA viruses (s.s....

This preview shows document pages 1 - 8. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online