Term
|
Definition
| A virus is a genetic element that cannot replicate independently of a living (host) cell. |
|
|
Term
|
Definition
| A virion is an extracellular form a virus. It contains nucleic acid surrounded by a protein coat and, in some cases, other layers of material. |
|
|
Term
| Characteristics of viral genomes |
|
Definition
- Viral genomes may either be DNA or RNA
- Some are circular, but most are linear |
|
|
Term
|
Definition
- Capside: the protein shell
- Capsomere: subunit of the capsid
- Nucleocapsid: complete complex of nucleic acid and protein packaged in the virion
- Enveloped virus: virus that contains a lipid membrane around the nucleocapsid |
|
|
Term
| What are some of the enyzmes that virions contain in order to infect their hosts? |
|
Definition
- Lysozymes: 1) makes a hole in the cell wall 2) lyses bacterial cells
- Nucleic acid polymerases
- Neuraminidases: Enzymes that cleave glycosidic bonds…allows liberation of virus from cells |
|
|
Term
| In what types of cells or organisms can viruses replicate? |
|
Definition
- Bacterial viruses are the easiest to grow and model; model systems
- Animal viruses (and some plant viruses) can be cultivated in tissue or cell cultures
- Plant viruses typically are most difficult because study often requires growth of the whole plant |
|
|
Term
| What are the steps of viral replication in animals? |
|
Definition
Attachment: Viruses attach to the cell membrane
Penetration: by endocytosis or fusion
Uncoating: by viral or host enzymes
Biosynthesis: Production of nucleic acid and proteins
Maturation: Nucleic acid and capsid proteins assemble
Release: by budding (enveloped viruses) or rupture |
|
|
Term
| Sense strand (+ strand) RNA virus |
|
Definition
- strand is transcribed from + viral genome
mRNA is transcribed from the – strand |
|
|
Term
| Antisense strand (- strand) RNA virus |
|
Definition
The + strand (mRNA) must first be transcribed from the – viral genome before proteins can be synthesized
Additional – strands are transcribed from mRNA
The – strands are later incorporated into the capsid |
|
|
Term
| Double-stranded RNA Virus |
|
Definition
mRNA is produced inside the capsid and released into the cytoplasm of the host
RNA polymerase initiates production of – sense strands. The mRNA and – strands form the dsRNA that is incorporated as new viral genome. |
|
|
Term
| Retroviruses characteristics |
|
Definition
RNA viruses
Replicate through an intermediate
Enveloped viruses
Contain a reverse transcriptase
Virion contains specific tRNA molecules
Have a unique genome: two identical ssRNA molecules of the plus (+) orientation
Contain specific genes:
- gag: encode for structural proteins
- pol: encode for reverse transcriptase and integrase
- env: encode for envelope proteins |
|
|
Term
| Different types of animal virus infections |
|
Definition
Acute infections: rapid onset, rapid decline
Persistent infections: release of virions from host cell does not result in cell lysis; infected cell remains alive and continues to produce the virus
Latent infection: delay between infection by the vrus an lytic events
Cell fusion: two or more cells becom one cell with many nuclei
Transformation: conversion of normal cell into tumor cell |
|
|
Term
|
Definition
Adenoviridae
Herpesviridia
Poxviridae
Papovaviridae
Hepadnaviridae |
|
|
Term
|
Definition
Retroviridae
- Viral RNA is transcribed to DNA, which can integrate into host DNA
- HTLV-1
- HTLV-2 |
|
|
Term
|
Definition
Bacteriophages are very diverse
Best studied bacteriophages infect enteric bacteria (E. coli and
Salmonella enterica)
Most contain dsDNA genomes
Most are naked
Structurally complex (heads, tails, and other components) |
|
|
Term
| Attachment and penetration of bacterial viruses |
|
Definition
Bacteriophage T4:
Attach to cells via tail fibers
Tail fibers retract
Lysozyme-like enzyme
Tail sheath contracts |
|
|
Term
| Bacteria virus life cycles: Virulent mode |
|
Definition
| Viruses lyse host cells after infection |
|
|
Term
| Bacteria virus life cycles: Temperate mode |
|
Definition
| Viruses replicate their genomes in tandem with host genome and without killing the host; virus can also be lytic |
|
|
Term
|
Definition
Infectious proteins whose extracellular form contains no nucleic acid
- Known to cause disease in animals (transmissible spongiform encephalopathies)
- Host cell contains gene (PrnP) that encodes native form of prion protein that is found in healthy animals
- Prion misfolding results in neurological symptoms of disease (e.g., resistance to proteases, insolubility, and aggregation) |
|
|
Term
| Prions mechanisms of disease |
|
Definition
Infectious prion disease: pathogenic form of prion protein is transmitted between animals or humans
Sporadic prion disease: random misfolding of a normal, healthy prion protein in an uninfected individual
Inherited prion disease: mutation in prion gene yields a protein that changes more often into disease-causing form |
|
|
