Virus Structure and Classification Flashcards Preview

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Flashcards in Virus Structure and Classification Deck (14)
1

Background and Significance of viruses

-all forms of life have viruses
-viruses and their hosts have co-evolved
-viral diseases have altered our history, ie AIDS, smallpox, influenza
-many of the concepts and tools of molecular biology have been derived from the study of viruses and their host cells
->4,000 viruses identified

2

Viruses as Filterable Agents

-homogenize the tissue
-then concentrate it through a filter- 220nm
-bacteria were trapped by the filter (filter becomes infection), viruses were not (filtrate remains infectious)

3

Virus size

-virsuses too small to be seen with light microscopes
-they are about 10^-7 - 10^-8
-requires tissue growth

4

Properties of viruses

-viruses are associated with all life forms
-viruses are obligate intracellular parasites
-definition of a virus: A capsid-encoding organism
-capsid: protein shell that encapsulates the nucleic acid genome
-virion: the particle encoded by a virus genome

5

Virus genomes are modular

-all viruses have 3 basic gene modules
1) capsid proteins
2) the replicon
3) Host interacting factors - multifunctional proteins that interact with the host, usually non structural because they are left behind in the infected cell and not packaged into the virion

6

Virus Structure

- helical or Icosahedral or complex symmetry capsid
-the capsid shape and genome type are independent
-enveloped virions obtain a lipid bilayer from the host cell
-naked virions lack an envelope

7

Virus Classification

Host Cell (Kingdom)
-Eukaryotic or Prokaryotic
-Plant, insect, animal

Genome Type:
-RNA or DNA
-Single or double stranded

Virion Structure
-enveloped or naked
-helical, isosahedral or complex

8

Virion Componenets

-Genome segments
-Nucleocapsid- protein that coats genome
-capsid or core
-tegument- the proteins around the capsid layer
-matrix
-envelope
-glycoprotein
spike or fiber

9

Virus survival strategy

1- the genome encodes a capsid that protects it outside the cell

2- the genome contains information for infecting a cell, replicating the genome, intracellular survival, and assembling virions

3- transmission to a new host is required to maintain the virus as a species

10

Adenovirus

-viral dsDNA
-icosahedral
-naked virus
-has fibers around outside
-Core proteins V, VII, and u, proteins VI and IX, protease, terminal protein

11

Poxvirus

-brick shaped
-enveloped
-outer and inner membrane
-dsDNA

12

Influenza virus

-enveloped
-helical
-segmented RNA
-HA and NA
-RNA polymerase

13

Retrovirus

-integrase, protease, reverse transcriptase
-gp120, gp41
-capsid shape changes from immature to mature
-enveloped
-dsRNA

14

Herpesvirus

-enveloped
-envelop proteins
-tegument- lots
-dsDNA
-isosahedral