Chapter 6
6 unique characteristics of viruses
1) have DNA or RNA, never both 2) tiny infectious particles, not cells 3) do not independently fulfill characteristics of life 4) multiply by taking control of host cell genetic material 5) lack enzymes for most metabolic processes 6) lack machinery for synthesizing protein
Cytopathic effects of viral infection include:
1) inclusions in the cytoplasm & nucleus 2) multinucleated giant cells 3) syncytia formation 4) cells round up
Viruses are used to produce vaccines for certain viral infections. T / F
True
Viruses cannot multiply outside a host cell. T / F
True
The nucleic acid of animal viruses enter the host cell through a. endocytosis b. fusion c. both a and b d. none of the above
c. both a and b
Enveloped viruses are released by a. endocytosis b. lysis of the host cell c. exocytosis d. fusion
c. exocytosis
A virus is a tiny infectious a. cell b. prokaryote c. particle d. nucleic acid
c. particle
Lysogeny refers to: a. altering the host range of a virus b. latent stage of herpes infection c. viral genome inserting into bacterial chromosome d. none of the above
c. viral genome inserting into bacterial chromosome
Plants are affected by virus like agents called a. virion b. satellite virus c. viroids d. prion
c. viroids
The nucleic acid of a virus is a. DNA only b. RNA only c. Both DNA and RNA d. Either DNA or RNA
d. Either DNA or RNA
Viral spikes: a. are always present on the viral envelop b. allow bacteria to evade host defense c. are derived from host proteins d. bind viral capsid and envelop together
d. bind viral capsid and envelop together
Classification of viruses involve all of the following except a. type of nucleic acid b. type of capsid c. presence of an envelop d. biochemical reactions
d. biochemical reactions
Viruses can not be cultivated in a. tissue culture b. bird embryos c. live mammals d. blood agar
d. blood agar
Helical and icosahedral are terms used to describe viral a. spike b. capsomer c. envelop d. capsid
d. capsid
The viral capsid is composed of protein subunits called a. spikes b. protomers c. virions d. capsomer
d. capsomer
Match A with B: A B 1) Lysogenic conversion a) Icosahedron 2) Enveloped virus b) Spongiform encephalopathy 3) Capsids c) Plant virus 4) Viroids d) Corynbacterium diphtheriae 5) Prions e) Exocytosis
1) D 2) E 3) A 4) C 5) B
Compare steps of viral multiplication cycles of bacteriophages and animal viruses
Bacteriophages -adsorption: Tail fibers attach to cell well of host -penetration: Injection of nucleic acid through cell wall, no uncoating -Synthesis: in cytoplasm -Persistence: lysogeny -Release: cell lyses when enzyme weaken Animal Virus -adsorption: attachment of capsid/envelope to cell surface receptors -Penetration: whole virus engulfed & uncoated or viral surface fuses with cell membrane, nucleic acid release -Persistence: latency, chronic infection, cancer -Release: lyses or exocytosis
A specific animal virus has the ability to attach to and enter almost any animal host cell. T / F
False
Adeno-associated virus and Delta agents are prions. T / F
False
Bacteriophages do not undergo adsorption to specific host cell receptors prior to penetration. T / F
False
Viruses are ultramicroscopic because they range in size from 2-450 um T / F
False
What dictates host range of animal virus? 2 ways animal viruses penetrate and leave host cell.
Host range dictated by receptor ligand specificity, cells that lack compatible receptors are resistant to adsorption/invasion by that virus. Animal viruses penetrate via fusion to membrane of host cell or endocytosis and exit via lyses or exocytosis.
Compare lysogeny and latency
Lysogeny- host chromosome carries bacteriophage DNA, infected host cell grow + reproduce for generations until they lyse. Prophage stays dorment in host until spontaneous lyses of cell releases prophage. Latency- viruses remain dorment in cells, sometimes year without activity, remain with the host cell and never released.
Prophages can be activated into viral replication and enter the lytic cycle. T / F
True
Compace virus, piron, and viroids
Virus- infectious particles, nucleic acid + capsid, sometimes envelope, causes many diseases. Prions- infectious proteins, no nucleic acid, no capsid, no envelope, cause spongiform encephalopathy in humans. Viroids- plant pathogen, no capsid, naked RNA strand, very small pathogens for important plants like tomato, cucumber, potatoes.
A prophage is an early stage in the development of a/an a. bacterial virus b. poxvirus c. lytic virus d. enveloped virus
a. bacterial virus
Infectious protein particles are called: a. prion b. viroids c. phages d. spikes
a. prion
In general, RNA viruses multiply in the cell-------, and DNA viruses multiply in the cell--------. a. nucleus, cytoplasm b. cytoplasm, nucleus c. vesicles, ribosome d. endoplasmic reticulum, nucleolus
b. cytoplasm, nucleus
Satellite viruses are a. also called viroids b. dependent on other viruses for replication c. the cause of spongiform encephalitis d. none of the above
b. dependent on other viruses for replication
T-even phages a. include the pox viruses b. infect the E.coli cells c. have helical capsids d. all of the above
b. infect the E.coli cells
An event that occurs in bacteriophage multiplication that does not occur during the multiplication of animal viruses is: a. adsorption to the host cell b. injection of viral nucleic acid into the host cell c. host cell synthesis of viral enzymes and proteins d. assembly of nucleocapsid
b. injection of viral nucleic acid into the host cell
Oncogenic viruses include all of the following except a. hepatitis B virus b. measles virus c. Epstein-Barr virus d. Papilloma virus
b. measles virus
The envelop of an animal virus is derived from the host cell' a. wall b. membrane c. glycocalyx d. receptors
b. membrane
Viruses have all of the following except a. genes b. metabolism c. definite shape d. ultramicroscopic size
b. metabolism
Clear patches in cell cultures that indicate sites of viral infection are called a. pocks b. plaques c. colonies d. prions
b. plaques
Enveloped viruses carry surface receptors called a. buds b. spikes c. fibers d. sheaths
b. spikes
These structures are used by bacteriophages to attach to host cell receptors a. sheath b. tail fibers c. nucleic acid d. none of the above
b. tail fibers
Host range is limited by: a. type of nucleic acid in the virus b. type of host cell receptors on the cell membrane c. age of the host cell d. size of the host cell
b. type of host cell receptors on the cell membrane
Infectious naked strands of RNA are called a. prions b. viroids c. spikes d. oncogenic viruses
b. viroids
