Classification and Taxonomy

Classification and Taxonomy Reference site: http://www.ncbi.nlm.nih.gov/ICTVdb/index.htm Naming viruses Animal viruses 1)Diseases that they cause: small pox, foot and mouth disease, hepatitis 2)Places where virus was first identified Norwalk virus, West Nile virus, Hanta virus 3) Other Organ virus was isolated from: adnoids -Adenovirus Sin Nombre Plant viruses an many insect viruses (two components) 1) Host 2) Disease Tomato bushy stunt virus Cricket paralysis virus 3 Classification and Taxonomy Classical: morphology Physical and chemical composition Genetic relatedness Modern: Phylogenetic, based on nucleic acid sequence analysis. 1. Disease symptoms Useful in clinical situations 2. Host organism implies a fixed link between virus and host-Small pox, HBV 3. Physical structure of the virus particle Envelope vs no envelope Helical or isocahedral Alls these approaches fail to predict fundamental features of the viruses Classical criteria for classification of animal viruses Modern Criteria for classification Based on genome composition and structure allows you to: 1) deduce the basic steps that must take place to produce mRNA 2) simplifies comprehension of the life cycle of virus Baltimore classification Traditional classification generate thousands of distinct entities but based on genomes can be classified into 7 groups [...]... nucleic acids - encode only nonstructural proteins or no proteins at all – rely upon a helper virus for replication, and caspid formation – often found in plants DI Particles Defective interfering particle: A virus that lacks part of its genome and interferes with the replication of a standard virus 1 Require helper virus 2 Derived from helper virus: They tend to be deletion mutants that have lost their... whose phenotype differs from original wild type strain but where the genetic basis for the difference is not known Special cases Satellites,DI particles,viriods & prions Satellites and viriods-subviral agents Satellite virus and nucleic acids Common features : 1) do not encodes enzymes required for replication 2)therefore require coinfection with a conventional (helper) virus 3) Satellite genome is significantly... geographical location • Not italicized Examples: – poliovirus – human immunodeficiency virus – West Nile virus Taxonomy: two examples Example 1: herpes simplex virus 1  Family: Herpesviridae or herpesvirus family  Subfamily: Alphaherpesvirinae; Genus: Simplexvirus; » Species: herpes simplex virus 1 Taxonomy: two examples Example 2: Poliovirus  Family: Picornaviridae or picornavirus family;  Subfamily: . (HCV) Flavivirus 5 NTR Structural Non-Structural 3’ NTR C prM 1E 2 B 3 B 5AA 4 cap 1) Hepacivirus AC E1 E2 2p7 3 B A B IRES Structural Non-Structural 3’ NTR 5 NTR 4 5 3) Pestivirus AN pro C. genome Present totals: Family: 73 Subfamily: 9 Genus: 287 Species: 1 950 Taxonomy scheme Family • A group of genera with common characteristics. • Capitalized,