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Chapter 13A: viruses, viroids, and prions
Terms in this set (48)
100 years ago viruses were described as "contagium vivum fluidum", what does this mean? When was the word virus first used and what did it mean back then? In 1935, tobacco mosaic virus was named by who?
-1930s and poison
What are viruses? Are viruses living entities? Are viruses living organisms? Can viruses be reproduced or produce protein without a living host? How many enzymes do viruses have of their own for metabolism or protein synthesis? Do viruses undergo cell division? How do viruses replicate? What is lab growth only possible in (3)? Can every type of living organism be infected by a virus?
-obligate intracellular parasites
-few or none
-by assembling themselves inside the host cell
-animals, embryonated chicken eggs, or cell/tissue cultures
What 2 main structures do all viruses have?
-single type of nucleic acid
-protein coat (capsid)
Single type of nucleic acid in viruses have viral proteins that are encoded by what (2)? Single type of nucleic acid in viruses are single stranded, double stranded or both? Single type of nucleic acid in viruses are linear, circular, or both? What is the viral genetic material range for nucleotide pairs? How many nucleotide pairs does E. coli have?
-DNA or RNA
-they can be either
-they can be either
-few thousand to 250,000
What is the protein coat (capsid)? What is the protein coat (capsid) coded for by? What does the protein coat (capsid) give the virus? What is the protein coat (capsid) made of?
-protective coat that surrounds the nucleic acid
-the viral genome
Are viruses naked, enveloped or both?
they can be either one
In enveloped viruses, what does the outer lipid bilayer cover? What does the enveloped virus come from and when? What do many enveloped viruses contain and what do those things do?
-host cell membrane during budding
-attachment spikes that project
In naked viruses (nonenveloped) what is the outer coat? What do naked viruses (nonenveloped) usually do and when?
-lyse the host cell when released
What are common morphological shapes (4)?
In the helical shape, where is the nucleic acid found? What are 2 viruses that have a helical shape?
-hollow, cylindrical capsule
-rabies and ebola
Is the polyhedral shape the most or least common? Is it many or few sided? How many triangular faces and corners does it have? What 2 viruses that have a polyhedral shape?
-20 triangular faces and 12 corners
-adenovirus and poliovirus
What 2 shapes does a complex shape consist of? What type of virus has a complex shape and what do they do?
-helical and polyhedral
-bacteriophages=viruses that infect bacteria
In spherical shapes, (non enveloped/enveloped) viruses are covered with what? What does this cause them to look spherical in?
Are viruses very small or big? What type os microscope is needed to see viruses?
Can any virus infect any type of cell?
What is a host range?
the spectrum of host cells the virus can infect
Can any type of living cell be infected with a virus? Most viruses can infect specific types of cells of only ____ host species. What determines if the virus can infect the cell or not?
-the receptors on the cell surface
How are enteric viruses usually transmitted? What do they usually cause? Where do some replicate and what do they cause?
-oral-fecal route (ingested)
-in the intestines and cause systemic disease (poliovirus)
How are respiratory viruses usually received? Where do they remain localized in?
-by inhaling in infected respiratory droplets
-in the respiratory tract
Where are zoonotic viruses transmitted from and too? What accidental hosts? What are they not usually transmitted from and to? How may they be transferred?
-animal to human or to another animal
-human to human (rabies)
-through vectors like arthropods
What do sexually transmitted viruses cause and where (2)? What are 2 ex. of sexually transmitted viruses? What other 2 things may they cause?
-cause lesions on genitalia or in genital tract (Herpes and Papilloma)
-systemic infections (HIV) or hepatitis
What 3 living animals are used when growing animal viruses in a lab? Can all viruses be grown in animals? If they can be do they always cause disease?
-mice, rabbits, and guinea pigs
How are animal viruses grown in embryonated eggs in the lab (2)? This used to be the most common method, what is the method still used to grow viruses for?
-hole drilled in shell and then the virus/tissue is injected into the fluid,
What is the preferred type of growth medium when growing animals viruses in a lab?
What is the cytopathic effect of viruses?
cells deteriorate as viruses multiply
In all phage infections, what enters the host cell? In a bacteriophage infection, where does the protein coat remain? In bacteriophage infections, what is used to make new capsid proteins assemble into new phage? What are the 2 types of life cycles of bacteriophage infections?
-the phage nucleic acid
-outside of the host cell
-phage nucleic acid
-lytic and lysogenic
What happens in the lytic cycle of a bacteriophage? What are the 5 steps of the lytic cycle?
-new virus is being made and released
In the lytic cycle, what happens during attachment?
phage attaches to the host cell
In the lytic cycle, what happens during penetration (2)?
phage penetrates host cell and injects DNA
In the lytic cycle, what does phage DNA direct during biosynthesis?
synthesis of viral components by the host cell
In the lytic cycle, what happens during maturation?
viral components are assembled into virions
In the lytic cycle, what happens during releases (2)?
-host cell lyses
-new virions are released
How do temperate phages live with their host bacteria in lysogeny?
When the phage enters the host cell they direct a _______ _________ (produce new _______) and incorporate their _______ into the host cell ________ (the ________ ________).
-lytic cycle, virus
-DNA, genome, lysogenic cycle
In lysogeny, _______ _____ becomes integrated into the ________ of the _____ ______ and replicates with the _____ ______.
In one result of lysogeny, what happens to lysogenic cells?
they're immune to reinfection by the same phage
In another result of lysogeny, phage conversion happens, what does this mean?
host cells may show new properties or physical characteristics
In another result of lysogeny, what can occur?
What is specialized transduction only carried out by and what happens when it is?
temperate phages and integrates into the host
During specialized transduction, when phage DNA leaves the bacterial chromosome what happens?
it takes chromosomal DNA with it
In specialized transduction, what will the virus be packaged with and where will it be transferred it?
packed with some bacterial chromosome which will be transferred to the next host cell
What system does bacterial defense use?
restriction modification system
Phage DNA entering a cell will be degraded by _________ _________ unless it has the same pattern of __________ as its own ____________ _____.
Do restriction enzymes degrade unmethylated DNA? Do restriction enzymes degrade methylated DNA?
Viruses can be grouped into families based on what (2)?
genomics and structure
What word is the gene name? What word is used for family names? What do order names end in?
A viral species is a group of viruses that share the same what (2)? What are subspecies written as and what is an ex.?
-genetic info and ecological host range
-numbers, ex. HIV-1
What virus is a cause of the common cold?
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