Viruses, Viroids, & Prions Deck (E4) Flashcards
What are the 5 key viral features?
1) Obligate intracellular pathogen
2) Host range
3) Acellular
4) Nucleic acid
5) Protein coat (capsid)
According to the International Committee on Taxonomy of Viruses (ICTV), what are the 3 factors determining a virion?
1) Developed, infectious, viral particle
2) Elementary bio-systems
3) Classified into orders, families, genera, and species
What are the 4 primary means of classifying a virus?
1) Genome composition
2) Replication & mRNA expression
3) Capsid morphology
4) Host range
When isolating and cultivating a virus, it must be grown in…
Living cells
Phages are cultivated in { } cultures, forming { }.
1) Bacterial
2) Plaques
Animal viruses were historically grown in…
Animals or embryotic eggs
Animal viruses are NOW grown in…
Cell cultures (whether primary or continuous “HeLa” cell lines)
Name the 2 methods used to identify virions.
1) Serological
2) Molecular
Bacteriophages go through a lytic and lysogenic cycle. What is the difference?
Lytic - phage causes cell to burst and host cell dies
Lysogenic - phage incorporate into host genome
Which cycle is a bacteriophage considered a prophage? Lytic or lysogenic?
Lysogenic
Name the 5 steps of the bacteriophage lytic cycle (HINT: Amanda Pulled Brian’s Mother, Rhonda).
1) Attachment
2) Penetration
3) Biosynthesis
4) Maturation
5) Release
What are 3 benefits to lysogeny?
1) Re-infection immunity
2) Phage/lysogenic conversion
3) Specialized transduction
Explain the 2 key steps a DNA virus performs to multiply.
1) Use host DNA polymerase after viral genome enters cell to make more of itself
2) Use host RNA polymerase to form mRNAs that are translated into capsid proteins
What is the difference between positive-sense ssRNA (+ssRNA) vs. negative-sense ssRNA (-ssRNA) viruses?
Positive-sense (coding) can be directly translated to protein while negative-sense (non-coding) has to be transcribed to positive-sense before translating to protein
How do dsRNA viruses multiply?
The dsRNA unwinds into positive and negative-sense strands. Positive translates proteins. Negative polymerizes w/ positive via viral RNA polymerase to renature the dsRNA.
How does a retrovirus multiply? List in 2 steps.
1) The RV’s RT converts its +RNA to dsDNA, which incorporates into host genome
2) Host RNA polymerase II transcribes viral DNA to RNA, which translates to more RT, glycoproteins, and capsid proteins
What is the difference between naked and enveloped viral release?
Naked - exocytosis or lysis
Enveloped - budding
What is the difference between latent and persistent viral infections?
Latent - remain dormant for a long time
Persistent - disease progresses over a long time
What is the major difference between a virus and a viroid?
Viroids don’t have protein coats, and can only infect plants with defective membranes. Also, viroids can’t recognize healthy cells without the protein coat
A proteinaceous infectious particle.
What is a prion?
What type of disease does a prion cause?
Spongiform encephalopathy
Name 4 diseases caused by prions.
1) Mad cow
2) Kuru
3) Scrapie
4) Creutzfelt-Jakob
How does a regular cellular protein differ from an infectious prion?
Normal proteins tend to have 3 alpha helices and 1 beta sheet while infectious prions tend to have a higher beta-sheet content that causes improper protein folding, leading to brain issues
