Micro Chapter 5
3 ways in which viruses are cultivated
-animal inoculation : some viruses can exhibit some host specifically -bird embryos: early developmental stage for animals - cell an tissue cultures :of host cells grown in special sterile chambers contaning correct types of proportions of growth factors
List the three principal purposes of cultivating viruses
-isolate and identify viruses in clinical specimens -prepare viruses for vaccines -do detailed research on viral structure, multiplication cycles, genetics, and effects on host cells
Temperate phage
A bacteriophage that enters into a less virulent state by becoming incorporated into the host genome as a prophage instead of in the vegetative or lytic form that eventually destroys the cell.
Lysogenic conversion
A bacterium acquires a new genetic trait due to the presence of genetic material from an infecting phage.
Oncogenic
A naturally occurring type of gene that when activated can transfer a normal cell into a cancer cell.
Capsid
A protein covering of a virus's nucleic acid core. Capsids exhibit symmetry due to the regular arrangement of subunits called capsomers
Icosahedral
A regular geometric figure having 20 surfaces that meet to form 12 corners. Some virions have capsides that resemble icoshedral crystals.
Capsomeres
A subunit of the virus capsid shaped as a triangle or disc
Bacteriophage
A virus that specifically infects bacteria.
Viroid
An infectious agent that unlike a virion, lacks a capsid and consists of a closed circular RNA molecule. Although known virods are all plant pathogens, it is conceivable that animal versions exist.
Diagram the five-step life cycle of animal viruses
Attachment: Exact fit between attachment proteins and receptors on cytoplasmic membrane Entry: Direct penetration, membrane fusion & endocytosis Synthesis: make more nucleic acid (virus) Assembly: new capsids and new nucleic acids Release: enveloped-budding; naked-exocytosis or lysis
Virion
Complete, fully developed virus particle Nucleic acid genome is either DNA or RNA
Transmissible spongiform encephalopathy (TSEs)
Diseases caused by proteinaceous infections particles (also known as prions)
Distinguish between enveloped and naked viruses
Enveloped: composed of phospholipid bilayer and proteins which often play role in host recognition; released by budding Naked: released by exocytosis or lysis
Helical
Having a spiral or coiled shape.
Explain the importance of viral surface proteins, or spikes
Host recognition; attachement
Transformation
In microbial genetics the transfer of genetic material contained in "naked" DNA fragments from a donor cell to a competent recipient cell.
Prion
Infectious protein(s) These diseases can be inherited genetic disorders transmitted by ingestion or contaminated nerve tissue transplants and surgical instruments Manifested as spongiform encephalopathies: human and animal
Naked Virus
No envelope
Describe the fx and structure(s) of viral capsids.
Outer coating; protect nucleic acid; attachment to host's cell; 3 shapes- Helical (spiral) Polyhedral (spherical) Complex (various
Obligate intracellular parasite
Require living host cells to multiply. Contain either DNA or RNA as genetic material. The genetic material is encased by a protein coat. Some have an envelope (membrane) that may contain protein spikes. Most viruses infect only specific types of cells in a single host
Complex virus
T4 bacteriophage
Genome
The complete set of chromosomes and genes in an organism.
Cytopathic effects
The degenerative changes in cells associated with virus infection. ex: multinucleated giant cells (Negri bodies). The prominent cytoplasmic inclusions of nerve cells infected by rabies virus.
Release
The final step in the multiplication cycle of viruses in which the assembled virus particle exists the host cell and moves onto infect another cell.
Lysogeny
The indefinite persistence of bacteriophage DNA in a host without bringing about the production of virions.
Host range
The limitation imposed by the characteristics of the host cell on the type of virus that can successfully invade it.
Uncoating
The process of removal of the viral coat and release of the viral genome by its newly invaded host cell.
Induction
The process whereby a bacteriophage in the prophage state is activated and begins replication and enters the lytic cycle d
Assembly
The step in viral multiplication in which capsids and genetic material are packaged into virions.
Synthesis
The step in viral multiplication in which viral genetic material and proteins are made through replication and transcription/translation.
Penetration
The step in viral multiplication in which virus enters the host cell.
Lysogenic
Viral DNA is incorporated into host DNA, creating a prophage When the cell replicates its chromosomes, it also replicates the prophage DNA May cause Phage conversion
Lytic
Viral nucleic acid destroys hosts DNA Uses host to assemble new viruses Causes cell tu burst and viruses to find cells
Diagram the possible nucleic acid configurations that viruses may posses.
[DNA] Double-stranded and Single-stranded _______________________________ [RNA] Single-stranded (+) polarity, Single-stranded (-) polarity, Double-stranded RNA, Single-stranded RNA reverse transcriptase.
Identify better terms for viruses than alive or dead
active or inactive
Spikes
carbohydrate-protein complexes, surface protrusions , attachment to cells.
Persistent infection
disease process occurs over a long period; generally is fatal (i.e.: HIV and Hep B)
Provide thorough descriptions of both lysogenic and lytic bacteriophage infections
lyosgenic: the host chromosome carries bacteriophage DNA lytic: the host cell becomes so packed with viruses that it lyses-splits open-thereby releasing the mature virions
Negative sense RNA Nucleocapsid
negative sense RNA viruses must undergo ________ before they can be translated transcription into mRNA what is required for make viral RNA into mRNA RNA dependent
Viral envelope
part of a cell membrane that goes outside the capsid. helps to disguise the virus
Discuss both persistent and transforming infections
persistent: can last from a few weeks to the remainder of the host's life transforming: enter a host cell and permanently alter its genetic material, leading to cancer
Tropism
specificity of a virus for a particular host tissue, determined in part by the interaction of viral surface structures with receptors present on the su
Provirus
the genome of a virus when it is integrated into a host cell's DNA.
Adsorption
to attach
Inert
unable to move
Describe three ways in which viruses are cultivated.
using bird embryos, using live animal inoculation, and using cell (tissue) culture techniques
discuss the primary reason that antiviral drugs are more difficult to design than antibacterial drugs
viral infections are difficult to treat because the drugs that attack viral replication also cause side effects in the host .
Positive sense RNA
viral mRNA that is directly translated into protein
Active Virus
virus enters the cell and is active
Latent
virus remains in asymptomatic host for long periods before signs and symptoms occur (i.e.: cold sores, shingles)
Define the term cytopathic effect and provide one example
virus-induced damage to the cell that alters its microscopic appearance ex. the fusion of multiple host cells into single large cells containing multiple nuclei
analyze the relative importance of viruses in the human infection and diseases
viruses are responsible for several billion infections each year. it is conceivable that many chronic diseases of unknown cause will eventually be connected to viral agents
Discuss the size of viruses relative to other microorganisms
viruses represent the smallest infectious agents (with some unusual exceptions)
Explain what it means when viruses are described as filterable
when infectious fluids from host organisms are passed through porcelain filters designed to trap bacteria, the filtrate remains infectious