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57 Cards in this Set

  • Front
  • Back

Viruses are obligatory _____________ parasites.

intracellular

Host range refers to the spectrum of _______ ______ in which a virus can multiply

host cells

_________ _________ is determined by the specific attachment site on the host cell’ssurface and the availability of host cellular factors.

host range

Viruses range from 20 to 1000 ___ in length.

nm

A ________ is a complete, fully developed viral particle composed of nucleic acidsurrounded by a coat

virion

Viruses contain either ________ or _________, never both, and the nucleic acid may besingle- or double-stranded, linear or circular.

DNA or RNA

The protein coat surrounding the nucleic acid of a virus is called the ____________.

capsid

The capsid is composed of subunits, _______________, which can be a single type ofprotein or several types.

capsomers

The capsid of some viruses is enclosed by an _________ consisting of lipids, proteins,and carbohydrates.

envelope

Some envelopes have protein complexes embedded in their surface called __________.

spikes

__________viruses (for example, Ebola virus) resemble long rods, and their capsids arehollow cylinders surrounding the nucleic acid.

Helical

___________viruses (for example, adenovirus) are many-sided. Usually the capsid isan icosahedron.

polyhedral

__________viruses have complex structures. For example, many bacteriophages have apolyhedral capsid with a helical tail attached.

complex

______________ of viruses is based on type of nucleic acid, strategy for replication, andmorphology.




a. Virus family names end in -_________; genus names end in -__________.




b. A viral __________ is a group of viruses sharing the same genetic informationand ecological niche.

Classification




a. Virus family names end in -viridae; genus names end in -virus.




b. A viral species is a group of viruses sharing the same genetic information and ecological niche.




Cultivation of some animal viruses requires whole ____________.

animals

Some animal viruses can be cultivated in ___________ eggs.

embryonated

______ __________ are cells growing in culture media in the laboratory.

cell cultures

Viral growth can cause _________ _________in the cell culture

cytopathic effects

______________tests are used most often to identify viruses.

Serological

Viruses do not contain ____________ for energy production or protein synthesis.

enzymes

For a virus to ___________, it must invade a host cell and direct the host’s metabolicmachinery to produce viral enzymes and components.

multiply

During the _______ cycle, a phage causes the lysis and death of a host cell

lytic

Some viruses can either cause lysis or have their DNA incorporated as a __________into the DNA of the host cell. The latter situation is called ______________.

prophage; lysogeny

During the ____________ (attachment) phase of the lytic cycle, sites on the phage’s tailfibers attach to complementary receptor sites on the bacterial cell ______.

adsorption; wall

During the ______________ phase, phage lysozyme opens a portion of the bacterial cellwall, the tail sheath contracts to force the tail core through the cell wall, and phage_______enters the bacterial cell. The phage __________ remains outside

penetration; DNA; capsid

In biosynthesis, transcription of phage DNA produces ______ coding for proteins necessary for phage multiplication.

mRNA coding

Phage _______ is replicated, and capsid proteins are produced.

DNA

During __________, phage DNA and capsids are assembled into complete viruses

maturation (assembly)

During __________, phage lysozyme breaks down the bacterial cell _______, and thenew phages are released.

release; wall

During the __________ cycle, prophage genes are regulated by a repressor coded for bythe prophage. The prophage is replicated each time the cell divides

lysogenic

Exposure to certain mutagens can lead to excision of the prophage and initiation of the_______ cycle.

lytic

Because of lysogeny, lysogenic cells become immune to reinfection with the same phageand may undergo phage ___________.

conversion

A lysogenic phage can transfer bacterial genes from one cell to another through______________.

transduction

Animal viruses attach to the _________ __________ of the host cell.

plasma membrane

Entry occurs by ______________ or ___________.

endocytosis or fusion

Animal viruses are ______ by viral or host cell enzymes

uncoated

The DNA of most DNA viruses is released into the _________ of the host cell.Replication and transcription of viral DNA produce viral ____ and viral _____. Capsidproteins are synthesized (translation) in the ____________ of the host cell.

nucleus, DNA, RNA, cytoplasm

DNA viruses include members of the families ___, ____, ____, ____ and _____

Adenoviridae, Poxviridae, Herpesviridae, Papovaviridae, and Hepadnaviridae

Multiplication of RNA viruses occurs in the _________ of the host cell.

cytoplasm

Retroviridae ___________ ___________ (RNA-dependent DNA polymerase) transcribesDNA from RNA

reverse transcriptase

After maturation, viruses are released. One method of release (and envelope formation)is ___________.

budding

Nonenveloped viruses are released through ruptures in the host cell membrane, (cell________).

lysis

When activated, _______transform normal cells into cancerous cells.

oncogenes

Viruses capable of producing tumors are called __________ viruses.

oncogenic

The _________ material of oncogenic viruses becomes integrated into the host cell’s DNA.

genetic

Oncogenic viruses are found among the Adenoviridae, Herpesviridae, Poxviridae,Papovaviridae, and Retroviridae

The Epstein-Barr Virus, a herpesvirus, causes _______ lymphoma and nasopharyngealcarcinoma. Hepadnavirus (HBV) causes _________ cancer

Burkitt's; cervical

Among the RNA viruses, only ___________ seem to be oncogenic.

retroviruses

_____ and _____ have been associated with human leukemia and lymphoma.

HTLV-1 and HTLV-2

The virus’s ability to produce tumors is related to the production of reverse transcriptase.The DNA synthesized from the viral RNA becomes incorporated as a _________ into thehost cell’s DNA.

provirus

A provirus can remain latent, can produce viruses, or can ___________ the host cell.

transform

A _________ viral infection is one in which the virus remains in the host cell for longperiods without producing an infection, examples are cold sores and shingles.

latent

____________ viral infections are disease processes that occur over a long period andare generally fatal.

Persistent

_________ are infectious proteins first discovered in the 1980s

Prions

________diseases, such as CJD and mad cow disease, all involve the degeneration of________ tissue, the result of an altered protein; the cause can be a mutation or contact with an altered protein

Prion; brain

Plant viruses must enter plant hosts through ________ or with invasive __________,such as insects. Some plant viruses also multiply in insect (vector) cells.

wounds; parasites

_________ are infectious pieces of RNA that cause some plant diseases, such aspotato spindle tuber viroid disease.

Viroids