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27 Cards in this Set

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Definition of Viruses
Obligate intracellular Parasite
Characteristics of Viruses
Unable to exist independently from host cells. Can direct life processes of host cells. Contain a sngle type of nucleic acid (DNA or RNA) and a protion coat, sometimes enclosed by an envelope composed of lipids, proteins, and carbohydrates
What does obligate mean?
Absolutely must
Size of Viruses
Smallest infectious agents must have electron microscopes to see. From 20nm to 450 nm in diameter
Components of a virus particle
A Cellular contains only the parts needed to invade and control a host cell.
2 main components of a virus particle
Central Core and External Covering
Central core contains?
Nucleic acid and preformed enzymes.
Characteristics of the Nucleic acid in a virus?
has DNA or RNA not both. genome (genes of organism) size is very small.
What are the minmum genes contained in the Nucleic acid in a virus?
Capsid synthesis, nucleic acid synthesis, regulation of host processes (home invasion gene) and virus packaging
Do all Viruses contain preformed enzymes?
No
What are some examples of preformed enzymes that may exsist in viruses?
polymerases, replicases and reverse transcriptase
What is the external covering of a virus called?
Capsid
What is the Capsid?
Protein "shell" that surrounds and protects nucleic acid. Helps introduce nucleic acid into host. Stimulates immune system.
What is a "nucleocapsid"?
Capsid and Nucleic acid equals "nucleocapsid"
What are subunits of Capsids called?
Capsomers they self assemble to form helical or icosahedral structures
What is the virus envelope?
External layer in some viruses. Derived from host cell membrane when viruses are released. Glycoprotein "spikes" on outside of envelope play a role in attachment of viruses to host cells.
Two requirements for viral multiplication
requires a host cell and viruses must be able to appropriate the synthetic and genetic machinery of host
Steps in Viral Multiplication
Adsorption, Penetration, Replication, Assembly and Maturation and Release
What is a Bacteriophage?
Viruses that infect Bacteria
What are the 2 multiplication cycles in Bacteriophages?
Lytic Cycle and Lysogeny
What is the Lytic cycle?
Replication of viral nucleic acids and proteins causes cell to be packed with virus. Causes lysis and death of host cell
What are the sequence of events in the lytic cycle?
Bacteriophage tail fibers bind to receptors on bacteria. Viral nucleic acid is injected through bacterial wall and membrane. Viral nucleic acid redirects genetic and metabolic activities of cell. Viral subunits spontaneously assemble. Host cell lyses liberating virions.
What is the main difference in Lytic cycle and Lysogeny?
"temperate" bacteriophages undergo adsorption and penetration but are not replicated or released. Host cell is not lysed
Lysogeny is equal to?
Latency
Examples of Lysogenic phages are?
Herpes Viruses, cold sores shingles
Other characteristics of lysogeny are.
Viral DNA is inserted into bacterial chromosome. Prophage is retained by bacterial cell and is copied during cell division. progeny also carry temperate phage. Viral genome is not expressed. Prophage in lysogenic cell can be excised from host chromosome and initiate lytic cycle.
A complete, fully developed viral particle composed of nucleic acid surrounded by a coat is known as?
Virion