Virus

Virus
Characteristics
Genetic Material: Either DNA or RNA
Can't replicate without a host cell
Can't divide by binary fission, Mitosis or Meiosis
Can't make energy (get it from Host cell)
Can't make their own Protein or Genetic material (steal it from host cell)
Intracellular Parasites
Size range from 10-300 nm
Can infect all Organisms
Genetic Material surrounded by Capsid or Protein coat (Small protein units called Capsomeres)
Some have an outer envelope
May also have tail, sheath and tail fibres
Classification
Type of genetic Material
shape and/or size of Caspid
Number of Capsomeres
Presence or absence of an envelope
Type of hosts it infects
Type of disease it produces
Target cell
Immunologic or antigenic properties
Host Range
Is the spectrum of host cells the virus can infect
Mostly single host range
Invertebrates
Vertebrates
Plants
Protists
Bacteria
Fungi
Rarely cross the hist range Barrier
Determined by
Attachment sites on the host
Availability in the potential host the factor for viral replication
Origin
3 Major theories
Viruses are remnants of past infections
Cells came before viruses
Viruses are degenerate cells or cell fragments
Viruses represent a separate evolutionary branch
Attachment sites
Outer surface of virus interact with specific receptor sites on surface of potential host cell
Complementary component held together by hydrogen bonds
Antiviral agents
Interfere with the Phases of viral multiplication
May disrupt an enzyme or protein
May interfere with the synthesis of viral parts like DNA, RNA or Protein synthesis
Some Viruses
Retroirus
Genetic information is single stranded RNA
Have a special enzyme called Reverse Transcriptase
Makes DNA from RNA
Integrate their newly formed double stranded DNA into the host cell
Many Retroviruses are responsible for junk DNA in our genome
Plant Virus
Bacteriophage
Viruse that infects Bacteria
Types
Virulent Bacteriophage
Causes lytic cycle
Steps
Attachment
Penerration
Biosynthesis
Assembly
Release
Temperate Bacteriophage
Do not immedietly begin lytic cycle
DNA remains embedded in Bacterial cell Chromosome
Animal Viruses
Attach to Specific binding sites on cells
This affects what species and which cell type is infected
Multiplication of Animal Viruses
Attachment
Penetration
Uncoating
Biosynthesis
Assembly
Release
Oncogenic Viruses
Viruses that cause cancer
Taxonomy
Based on guideline by ICTV (International Committee on Taxonomy of Viruses)
Grouping based on
Nucleic acid type
Strategy of replication
Mosphology
Names
Older names: end with - ales
Family Name: end with- Viridae
Genus Name: End with - Virus
Species name: Described by common name
Subspecies name:Designated by number
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