MIDTERM 1/4

Virion

Complete infective virus particle; may be identical to the nucleocapsid.

Viroids

smallest infectious agents causing disease in plants

Nucleocapsid

The capsid together with the enclosed nucleic acid.

Capsid

Protein shell that encloses the nucleic acid core.

Capsomeres

Morphologic units seen on the surfaces of icosahedral virus particles; represent clusters of structural units.

Envelope

Outer coat some viruses acquire as they penetrate or are budded from the nuclear or cytoplasmic membrane; always contain altered host-cell membrane components.

Peplomers

Morphologic units composed of structural units embedded in the envelope.

Bacteriophages

Viruses that infect bacterial cells.

Complementation

general term to describe

situations where mixed infections result in

enhanced yields of one or both viruses in the

mixture

Translation

Mechanism by which a particular base sequence in messenger RNA produces a specific amino acid sequence in a protein.

Transcription

Means by which specific information encoded in a nucleic acid chain is transferred to messenger RNA.

Helper virus

Required by certain defective closely related viruses to replicate.

Defective virus

Functionally deficient particles that may interfere with the replication of normal viruses.

Satellite viruses

Viruses that cannot reproduce from their own nucleic acid and are non-infectious; require a helper virus for transmission and multiplication.

true

All viruses are obligate intracellular parasites, however all obligate intracellular parasites are not viruses

Reverse Transcriptase

Enzyme that converts RNA into DNA.

Retroviruses

Viruses that require cellular transfer tRNAs for the reverse transcriptase reaction.

Inactivated viruses

Viruses that are sensitive to organic solvents and have an envelope.

Non-enveloped viruses

Viruses that are resistant to organic solvents.

International Committee on Taxonomy of Viruses

established in 1966 to classify viruses.

Baltimore classification system

Classification system for viruses based on genome type and mode of replication.

Positive sense RNA

RNA that is of the same sense as mRNA and is directly capable of translation to protein.

Negative sense RNA

RNA whose genomic nucleotide sequence is complementary to mRNA and requires transcription of the genome to generate mRNA equivalents.

Eclipse period

Time between the penetration of the virus particle into the host cell and the production of the first new virus particle.

Fill in the blank: The __________ is the protective outer layer of a viral particle that surrounds its nucleic acid.

Capsid

Fill in the blank: The __________ period is the time in which a virus is not detectable in the host despite ongoing infections.

Eclipse

Fill in the blank: __________ is the process by which a virus replicates and assembles new virions in a host cell.

Replication

Fill in the blank: __________ are viral particles that cannot independently replicate and require a helper virus for reproduction.

Satellite viruses

Fill in the blank: __________ is the enzyme responsible for the conversion of RNA into cDNA during reverse transcription.

Reverse Transcriptase

Fill in the blank: The __________ refers to a classification system that groups viruses by their type of nucleic acid.

Baltimore classification system

Fill in the blank: __________ viruses are generally more resistant to environmental factors than enveloped viruses.

Non-enveloped

virion?

A complete infective virus particle; may be identical to the nucleocapsid.

What does the nucleocapsid consist of?

The capsid together with the enclosed nucleic acid.

What primary function of the capsid?

It serves as the protein shell that encloses the nucleic acid core.

capsomeres

Morphologic units seen on the surfaces of icosahedral virus particles; represent clusters of structural units.

What is the role of the envelope in some viruses?

It is the outer coat acquired as they penetrate or bud from the nuclear or cytoplasmic membrane.

What are peplomers?

Morphologic units composed of structural units embedded in the envelope.

What defines a bacteriophage?

Viruses that specifically infect bacterial cells.

transcription process

The means by which specific information encoded in a nucleic acid chain is transferred to messenger RNA.

reverse transcriptase

It is the enzyme that converts RNA into DNA.

retroviruses

Viruses that require cellular transfer tRNAs for the reverse transcriptase reaction.