CH6 pt 2 Flashcards
- has only one option: to begin multiplying immediately upon entering its bacterial host, followed by release from the host by lysis
- destroys the host bacterial cells
lytic (virulent) phages
lytic cycle
- two options: upon entry into the host, they can multiply like virulent phages and lyse the host cell, or they can remain within the host without destroying it
- viral DNA integrates into bacterial chromosome
temperate (avirulent) phages
lysogenic cycle
viral nucleic acid either integrated into the bacterial chromosome or free in the cytoplasm
prophage
most bacterio phages are either _____ or ______
virulent or avirulent
number of phages produced by lytic and lysogenic cycle
lytic- aboout 100
lysogenic- none, bc genome replicates but no virions
The protein coat surrounding the viral genome is called the
capsid
Plant viruses can be transmitted
by insects, using mechanical abrasives, grafting one plant to another, fungi
Naked animal viruses most often gain access to eukaryotic host cells by
endocytosis.
Which diseases are caused by prions?
kuru and Creutzfeldt-Jakob Disease in humans, mad cow disease, scrapies in sheep
Which of these is incorrect regarding prions?
they are infectious proteins
they cause incorrect folding of normal proteins
they were first described in the early 1900s
they do not contain nucleic acid
they were first described in the early 1900s
Animal viruses have been cultivated in
- tissue cultures (monolayers of animal cells).
- suitable host animals.
- embryonated eggs.
- acellular
- can be observed with an electron microscope.
- can exist in an intracellular or extracellular phase
- replicate only inside host cells.
viruses
- a lytic infection most often yields one to two hundred virions
- they most often have a dsDNA genome
- they are most often naked
phages
has been associated with a form of liver cancer
hepatitis B virus
Viral capsid protein subunits are called
protomers
Viral capsids are generally constructed without any outside aid once the subunits have been synthesized
self-assembly.
A complete virus particle is called a
virion
Many of the enzymes found in virus particles are
involved in the replication of viral nucleic acid.
Most enveloped viruses use the host __________ membrane as their envelope source.
plasma
Cytopathic effects
are observable changes in cells due to viral replication
Prions are of significance because they cause infections of
domestic animals and humans.
Glycoprotein spikes protruding from the outer surface of viral envelopes function as
factors that bind to host cells.
Viroids are of economic significance because they cause disease in
plants
In the lysogenic cycle
the virus becomes a prophage
Virion size ranges from
10–400 nm.
Two major types of symmetry found in viruses include
icosahedral and helical
Human cancer causing viruses most often have a ___________ genome.
dsDNA
Which of the following is/are not true about viral envelopes?
The envelope proteins are virus specific.
They are typical lipid monolayers with embedded viral proteins.
They are typical lipid bilayers with embedded viral proteins.
The envelope lipids are derived from the host.
They are typical lipid monolayers with embedded viral proteins.
Which of the following is not true of plaques?
they result when viruses are cultured in chicken eggs
they vary is size and appearance based on virus replication rates
they can be used to count and isolate phage
they are clear zones on a lawn of bacteria
they result when viruses are cultured in chicken eggs
Prions are of significance because they cause infections of
domestic animals and humans
Bacterial viruses typically infect host cells
injecting their nucleic acid in host cell
describe the lytic cycle
In the lytic cycle, new virus particles are made and released when the host cell lyses. Virulent phages are limited to just the lytic cycle.
describe the lysogenic cycle
- The lysogenic cycle allows the genome of the virus to be replicated passively as the host cell’s genome is replicated.
- Certain environmental factors such as UV light can cause a switch from the lysogenic cycle to the lytic cycle.
Eukaryotic viruses can cause microscopic or macroscopic degenerative changes or abnormalities in host cells and in tissues that are distinct from lysis
cytopathic effects (CPEs)
characteristics of viruses associated with human cancers
dsDNA or become it when in the cell (retrovirus)
transformed cells have
uncontrolled growth, loss of normal function, and move to other sites (malignant)
___% of human cancers have a virus link
15%
how are human cancers associated with implications?
- most are dsDNA
- Hepatitis B (liver cancer), Herpes 8, HPV (cervical cancer)
- ssRNA
- HTLV (rare immunity), Hepatitis C
- many form a provirus
types of animal cultivation with advantages and disadvantages
-living animals
A- required for an immune response, virulence studies
D- expensive, labor intensive, contamination
-embryonate chicken egg
A- inoculated aseptically (less contamination)
D- can’t view immune responses
-cell/tissue culture
A- visible effects of virus on cells, no contamination
D- not cheap and can’t view immune responses
how has virology advanced
e- microscopes and cell culture
types of cultivation of plant viruses
whole plants and plant tissue culture
- vectors
- mechanical inoculation- carborundum (rub leave with abrasive)
- grafting- diseased plant onto healthy plant (natural inoculation
cultivation of a plant viruses in a whole plant
cultivation of bacteriophage
- find them where their host is found
- young actively growing bacteria culture
- solid media- plaques, used to count viruses, isolate and purify a virus
- broth- turbid broth becomes clear
clear zones- form from on a lawn of bacteria
plaques
- cause plant diseases
- ssRNA with no protein coat
viroids
interfere with mRNA processing and slicing of mRNA
viroid pathogenicity
- incorrectly folded proteinaceous infectious particles (no DNA or RNA)
- cause transmissible , slow progressing CNS disease
prions
what causes incorrectly folded protein in prions?
conformational changes are changing protein
