Lecture 13: Viruses, Viroids, and Prions Flashcards
What are the general characteristics of a virus?
- obligatory intracellular parasites
- contain DNA & RNA & protein coat
- no ribosomes
- no ATP generating mechanisms
What is the host range?
spectrum of host cells a virus can infect
- most viruses infect specific cells in 1 host
What is a bacteriophage?
viruses that infect bacteria
What are the 4 components of a viral structure?
Vivion: complete, fully developed viral particle
Capsid: protein coat of capsomeres
Envelope: lipid, protein, & carb coating on some viruses
Spikes: projections from outer surface
What are the 4 common general morphologies of a virus?
Helical viruses: hollow, cylindrical capsid
Polyhedral viruses: many sided
Enveloped viruses: lipid membrane derived from host cell
Complex viruses: complicated structures; variety of components in capsids
(relating to taxonomy of viruses)
What do the Genus, family and order names end in?
Genus names end in -virus
Family names end in -viridae
Order names end in -ales
What is a viral species?
group of viruses sharing the same genetic information and host
What would the order, family, genus, and species be of Covid-19?
order: nidovirales
family: coronaviridae
genus: coronavirus
species: SARS-CoV-2
How are bacteriophages grown in a lab?
- grown in bacteria
- form plaques
- each plaque corresponds to a single virus; can be expressed as plaque forming units (PFU)
How are animal viruses grown in a lab?
- living anials
- embyronated eggs
- cell cultures: can observe cytopathic effect (CPE)
What are different ways of viral identification/detection?
- cytopathic effect
- serological tests
- nucleic acids
- rapid tests
What tests could you use to identify influenza virus in a patient?
- rapid tests
- serological tests
What is required for a virus to multiply?
- invade a host cell
- take over hosts metabolic machinery
What is the one step growth curve?
indicate that virus particles in eclipse are responsible for replication
What is the lytic cycle involved in the multiplication of bacteriophages?
- phage causes lysis and death of the host cell
What are virulent pages and how do they relate to the lytic cycle?
- restricted to lytic infections
- rapid viral replication ends in progney release and bacterial death
What is the lysogenic cycle?
- phage DNA is incorporated in the host DNA
- phage conversion
specialized transudction
What are temperate phages and how does it relate to the lysogenic cylce?
- follow either a lytic or a lysogenic cycle
- in the latter, viral DNA maintains itself in the host as a prophage
What are the stages of multiplication?
attachment
entry
uncoating
either: chronic infection or biosynthesis
from biosynthesis: release
What is the biosynthesis of DNA viruses?
- DNA viruses replicate their DNA In the nucleus of the host using viral enzymes
What is adenoviridae? DNA or RNA virus?
double stranded DNA non enveloped viruses
- respiratory infections in humans
- tumors in animals
What is poxviridae? DNA or RNA virus?
double stranded DNA enveloped viruses
- cause skin lesions
- vaccinia and smallpox viruses
What is herpesviridae? DNA or RNA virus?
DB stranded DNA enveloepd viruses
HHV-(1-8)
What is papoviridae? DNA or RNA virus?
DBL stranded DNA, noneveloped
- causes warts
- can transform cells and cause cancer
What is hepadnaviridae? DNA or RNA virus?
DBL DNA, enveloped
- hepatitis B virus
- reverse transcriptase to make DNA from RNA
How do Viruses multiply in a host cells cytoplasm? What is ssRNA + & -, and dsRNA?
RNA-dependent RNA polymerase
-ssRNA; + (sense) strand: viral RNA serves as mRNA for protein synthesis
- ssRNA; - (antisense) strand: viral RNA is transcribed to a + strand to serve as mRNA for protein synthesis
- dsRNA: double stranded RNA
What is picornaviridae? DNA or RNA virus?
sngl stranded RNA virus
+ strand
nonenveloped
-entervirus: poliovirus & coxsackievirus
-rhinovirus: common cold
-hepatitas A
What is togaviridae? DNA or RNA virus?
sgl RNA
+ strand
enveloped
-alphavirus
-rubvirus
What is rhabdoviridae? DNA or RNA virus?
sgl RNA
- strand
ONE RNA strand
- lyssavirus: rabies
What is reoviridae? DNA or RNA virus?
DBL Rna
- nonenveloped
- reovirus (respiratory enteric orphan)
- rotavirus
What is a provirus?
form of a virus integrated into the genetic material of a host cell
Are cancers caused by viruses contagious?
no
What is sarcoma?
cancer of connective tissue
What is adenocarcinomas?
cancers of glandular epithelial tissue
What are oncogenes?
transform normal cells into cancerous cells
What do oncogenic viruses?
become integrated into the host cells DNA and induce tumors
What DNA viruses are oncogenic viruses?
adenoviridae
herpesviridae
poxviridae
papovaviridae
- human papillomavirus
hepadnaviridae
- hepatitis B virus
retroviridae
What is a latent virus?
remains in asymptomatic host cell for long periods
- may reactivate due to changes in immunity
+ cold sores (herpesvirus), chingles (varcella zoster virus)
What is a persistent viral infection?
occurs gradually over a long period; generally fatal
- measles virus
What are prions?
- PROteinaceous INectious particles
- inherited and transmissible by ingestion, transplant, & surgical instruments
- mad cow disease
