Viruses  What are they? and  What are they good for? (ebiomedia.com) (conference.eicar.org)

Structure of a virion RNA or DNA Protien capsid Icosahedral structure ( Nucleo- capsid ( Lipid bilayer Membrane protien

Life Cycle of a Virus Attachment Penetration Uncoating Replication & Expression Assembly Release

 Membrane or capsid proteins bond to cell receptors Attachment Penetration Uncoating Replication & Expression Assembly Release

 Permeation or  Injection of the genome or  Naked capsid swalllowed by the cell membrane or  Envelope integrated into cell membrane or  …. Attachment Penetration Uncoating Replication & Expression Assembly Release

 Capsid breaks  Genome and enzymes released. Attachment Penetration Uncoating Replication & Expression Assembly Release

 Viral genome replicated  Host cell mechanisms  Carry-along mechanisms  Protiens synthesized (Inhibition, Structure, Replication)  Host cell mechanisms Attachment Penetration Uncoating Replication & Expression Assembly Release

Virion assembled  In the cytoplasm  In the nucleus  At the cell membrane Attachment Penetration Uncoating Replication & Expression Assembly Release

Release of new viruses  Cell ruptures  Cell dies and membrane disolves  Virus ”buds” from the membrane Attachment Penetration Uncoating Replication & Expression Assembly Release

Example: Life cycle of a retrovirus Redisplayed without permission from W.H. Freeman publishing,

Viruses helps research into…  DNA replication  mRNA synthesis, translation and regulation  DNA replication  Polyproteins  Intracellular transport  Membrane formation  Cell transformation And of course…  Gene therapy and cloning (vectors)

The Central Dogma Baltimore and Temin: ”How can retroviruses cause cancer?” DNA RNAProteins

Baltimore & Temin Nobel Prize in Medicine or Physiology 1975  Retrovirus replication: ”Reverse transcriptase” Viral RNA → DNA Viral RNA → DNA Photos reproduced without kind permission from DNA RNAProteins The Central Dogma

Gene therapy  A ”viral vector” inserts genome into cells with defective genes.  Random integration  Swapping  Repairing  Regulation  Potential to treat deseases such as Cystic Fibrosis, Parkinsons, Alzheimers and cancers.

Gene Therapy Problems  Effects last for only 2-3 weeks  Immune response  Damages of random integration  Multigene disorders  Hard to produce viruses

Gene Therapy Research under way  Viruses that insert there genome at a specific location  A 47th chromosome  Vesicles carrying DNA