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