Ch 13 Viruses Nester Microbiology
lysogenic conversion
a change in the properties of a bacterium conferred by a prophage
titer
concentration of infectious phage particles in the original phage suspension
tumor suppressor genes
genes that inhibit cell growth
proto-oncogens
genes that stimulate cell growth
plaque assay
method used to measure the number of viral particles present in a sample by counting the number of plaques.
provirus
silent viral genome
filamentous phage
single stranded DNA phage that look like long fibers, these phages cause productive infections but the process does not kill the host cell. infected cells grow more slowly than uninfected cells.
matrix protein
the _________ __________ is located between the nucleocapsid and the envelope
nucleocapsid
the capsid plus the nucleic acid is called the...
T4
the most studied lytic phage
lambda phage
the most thoroughly studied temperate phage
replication of dsDNA
uses the host RNA polymerase to transcribe DNA
replication of ssDNA
in order to replicate a compliment single stranded molecule must be made, it will either be + or -,
primary culture
individual cells processed from removed animal tissue in a nutrient medium
viroid
infections agnt that consists only of RNA molecules, no protein coat
generalized transducing particles
phage heads that contain only bacterial genes instead of phage genes
budding
process where the virus acquires an envelope as it leaves the cell, this may trigger apoptosis
capsomere
protein subunits that make up the capsid, they are all identical, this allows for less genetic information and simple assembly instructions, saves room on the genome
specialized transduction
results from an excision mistake made by a temperate phage during its transition from a lysogenic to a lytic cell. It takes a piece of the chromosome with it. Now each virus takes the DNA with it, no need for homologous recombination.
replication of dsRNA
the process in which mRNA is synthesized off the virus genetic material, there must be a RNA dependent RNA polymerase or replicase.
capsid
the protein coat that covers the nucleic acid of a viral particle (virion)
10nm
the smallest virus is about how large?
-viridae
the suffix that represents a virus family
-virus
the suffix that represents the virus genus
Lysogenic infection
the type of infection where the virus inserts its DNA into the host cells genome. This cell is called a lysogen
helical
the virus shape that appears to be cylindrical, the capsomers are arranged in a helix
complex
the virus shape that had a more intricate structure, phages are the only viruses with this structure
icosahedral
the virus shape that has a 531 symetry, 20 small triangular facets.
lytic phages
these are virulent phages, they exit the host at the end of an infection lysing the cell. this type of infection is considered productive.
Temperate phages
these phages have the option of either directing a productive infection or incorporating their DNA into the host cell's genome (lysogenic infection). if the DNA is damaged the cell will go back into the lytic stage.
restriction modification systems
these protect bacteria from phage infection by quickly degrading incoming foreign DNA. They do this through restriction and modification enzymes.
integrase
this inserts the DNA into the cell chromosome in a lysogenic infection.
Chronic infections
this is a persistent infection characterized by continuous low level production of viral particles. (hep B, hep C, AIDS)
Latent Infection
this is a persistent infection where the viral genome (provirus) remains silent in the host cell, it can reactivate. (herpes, cyomegalovirus, HIV, epstein-barr virus)
Lysogen
this is the name of the cell where viral DNA has been integrated into its genome
generalized transduction
this results from packaging error during phage assembly. During packaging a piece of chromosome can be taken up instead of phage DNA. The piece of the chromosome can be taken up by a new host cell via homologous recombination
reverse transcriptase
this synthesizes DNA from the RNA template, it runs counter to the central dogma of molecular biology.
persistent infections
this type of infection can continue for years or even a lifetime. with or without symptoms
acute infections
this type of infection is charcterized by the sudden onset of symptoms and relatively short duration
naked virus
this type of virus is more resistant to disinfectants as it does not have an envelope.
retrovirus
this type of virus that has a +RNA genome and uses reverse transcriptase to make DNA from an RNA template.
productive infection
viral infection in which more viral particles are produced
latent infection
viral infection in which the viral genome is present but not active, so viral particles are not being produced
lytic infection
viral infection of a host cell with a subsequent production of more virus particles and lysis of the cell.
virion
viral particle that is made up of nucleic acid surrounded by a protein coat (capsid) ...a complete virus in its inert non-replicating form. also referred to as a viral particle
replicase
viraly encoded RNA, dependent on RNA polymerase that uses the RNA genome as a template to make complimentary copies
poison
virus means...
adenovirus
virus often used for gene replacement therapy,
lytic phage infection 5 step process
1. adsorption- this is where the phage attached to the cell. It binds to a receptor molecule 2. penetration- in prokaryotes only the nucleic acid penetrates the cell 3. gene expression and biosynthesis- the phage genome is transcribed and phage DNA is synthesized. 4. assembly- phage components are assembled 5. release- the progeny virus is released either through cell lysis or the new virus is extruded through the cell wall.
5 step process for the generalized infection cycle of animal viruses
1. attachment 2. penetration and uncoating- can be done via membrane fusion or endocytosis. the entire capsid is taken into the cell and it is then uncoated 3. gene expression and bisynthesis 4. assembly 5. release
repressor
a protein that prevents expression of the gene required for excision, it is essential for maintaining the lysogenic state.
cytopathic effect
a virus can cause the distinct morphological alterations in infected cells called....
enveloped viruses
a virus that has a bilayer envelope that surrounds the matrix protein
bacteriophages
a virus that infects a bacterial cell
tumor
abnormal growth of tissue resulting from a malfunction in the normally highly regulated process of cell growth.
malignant
abnormal mass of abnormal cells, can metastasize to other tissues
benign
abnormal mass of normal tissues, do not metastasize.
the viral genome
always either RNA or DNA but never both
prion
an infectious agent that causes a neurodegenerative disease; consists of protein similar in amino acid sequence to a normal protein. no nucleic acid, these are not viruses
lysogens
bacteria that carry prophage (phage DNA) in the genome.
oncogens
cells that can interfere with host control mechanisms and induce tumors
virus
genetic material surrounded by a protein coat, no metabolism, not alive,
Morphology of the virus
icosahedral, complex, and helical
replication of ssRNA
if you have the - strand you can make new genetic material right off the template, if not you have to make the - strand first.1