Ch.13
in ________, transcription of phage DNA produces mRNA coding for proteins necessary for phage multiplication. phage DNA is ______ and capsid proteins are _____.during eclipse period, separate phage DNA and protein can be found.
biosynthesis; replicated; produced;
After maturation, viruses are released. One method of release is _____. Nonenveloped viruses are released through ____ in the host cell membrane
budding; ruptures
Multiplication of RNA viruses occurs in the cytoplasm of the host cell. _______ synthesizes a double-stranded RNA
capsid
the protein coat surrounding the nucleic acid of a virus is called a
capsid
the capsid is composed of subunits, _____, which can be a single type of protein or several types
capsomers
The earliest relationship between cancer and viruses was demonstrated in the early 1900s, when chicken leukemia and chicken sarcoma were transferred to healthy animals by _____
cell-free filtrates
_____ viruses have complex structures. For example, many bacteriophages have a polyhedral capsid with a helical tail attached.
complex
persistent viral infections are caused by __________ viruses; viruses accumulate over a long period.
conventional
Capsid proteins are synthesized in ____ of the host cell.
cytoplasm
viruses contain either DNA or RNA, never both, and the nucleic acid may be single or double standed, _____ or ______ or _____ into several separate molecules
linear; circular; divided
viruses must be grown in _____.
living cells
some viruses can either cause lysis or have their DNA incorporated as a prophage into the DNA of the host cell. this is the ______ cycle
lysogenic
because of _______, ______ cells become immune to reinfection with the same phage and may undergo phage conversion.
lysogeny, lysogenic
During the ______, a phage causes the lysis and death of a host cell.
lytic cycle
During ______, phage DNA and capsids are assembled into complete viruses
maturaton
host range refers to the spectrum of host cells in which a virus can ______.
multiply
exposure to certain ______ can lead to excision of the prophage and initiation of the lytic cyle
mutagens
The DNA of most DNA viruses is released into ____ of the host cell. transcription of viral DNA and translation produce viral DNA and, later capsid proteins.
nucleus
When activated, __________ transform normal cells into cancer cells
oncogenes
viruses are obligatory intracellular _____.
parasites
in ________, phage lysozyme open a portion of the bacterial cell wall, the tail sheath contracts to force the tail core through the cell wall, and phage DNA enters the bacterial cell. The capsid remains outside
penetration
_______ viruses must enter plant hosts through wounds or with invasive parasites, such as insects. some also multiple in insect cells
plant
After several viral multiplication cycles the bacteria in the area surrounding the original virus are destroyed; the area of lysis is called a _________
plaque
________ resemble long rods, and their capsids are hollow cylinders surrounding the nucleic acid.
polyhedral viruses
______ diseases are the result of an altered protein; the cause can be a mutation in the normal gene for PrPc or contact with an altered protein.
prions
viruses contain a single type of nucleic acid (DNA or RNA) and a ______ coat
protein; envelope
animal virus entry occurs by _____ - mediated endocytosis or fusion
receptor
During ____ , phage lysozyme breaks down the bacterial cell wall, and the new phages are released.
release
___________are digested in host cell cytoplasm to release mRNA for viral biosynthesis
reoviridae
the _______ cycles of viruses differ among viruses and are determined by their unique structures and genomes
replication
Why are viruses grown in eggs and not in culture media?
there is no host
________ strand RNA acts as a template for RNA-dependent RNA polymerase, and mRNA is transcribed from a new - RNA strand
togaviridae +
The latter situation of the lysogenic cycle is specialized _____
transduction
animal viruses are _____ by viral or host cell enzymes
uncoated
_______ is a complete, fully developed viral particle outside a host cell
virion
Cultivation of some animal viruses requires _______
whole animals
____________ is one in which the virus remains in the host cell for long periods without producing an infection. Examples are ______ and ______
;cold sores; shingles
DNA oncogenic viruses::
Adenoviridae Herpesviridae Poxviridae Papovaviridae Hepadnaviridae
DNA viruses include members of the families :
Adenoviridae Poxviridae Herpesviridae Papovaviridae Hepadnaviridae
_____________ strand RNA is a template for viral RNA-dependent RNA polymerase, which transcribes mRNA
Rhabdoviridae -
______ are viruses that infect bacteria
bacteriophages
the easiest viruses to grow are _______
bacteriophages
viruses range from ____ to ____ nm in lenth
20; 1000
The genetic material of oncogenic viruses becomes integrated into the host cells' ______
DNA
viruses compromise genetic material either ______ or _______ surrounded by _________ and/or ____________ derived from a ________.
DNA; RNA; capsid; envelope; host's cell membrane
_____________ strand RNA acts as mRNA and directs the synthesis of RNA-dependent RNA polymerase
Picornaviridae +
How do latent and persistent infections differ?
The virus remains in the host cell for long periods without producing an infection in latent infections. The disease process occurs over a long period in persistent infections.
How do viroids differ from viruses?
Viruses contain a capsid while viroids do not contain a capsid.
_______ viruses attach to the plasma membrane of the host cell.
animal
Some animal viruses can be cultivated in embryonated ______
eggs
________ viruses are covered by an envolope and are roughly spherical but highly pleomorphic. There are also enveloped helical viruses and enveloped polyhedral viruses.
enveloped
the capsid of some viruses is enclosed by _______, consisting of lipids, proteins, and carbohydrates.
envelopes
viruses do no contain _____ for energy production or protein synthesis
enzymes
some envelopes are covered with carbohydrate-protein complexes called
helical viruses
most viruses ____ only specific types of cells in one host species
infect
Viruses to treat cancer: oncolytic viruses _____and ______the cancer cells
infect; lyse
for a virus to multiply, it must _____ a host cell and direct the host's metabolic machinery to produce viral enzymes and components
invade
A provirus can remain _______, can produce viruses, or can transform the host cell.
latent