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